A41A-0004 

Comparison of Clear Sky OLR from AIRS and CERES Observations

* moy, l (lesliem@ssec.wisc.edu), Space Science and Engineering Center, U of Wisconsin, 1225 W. Dayton St, Madison, WI 53713, United States Borg, L (lori.borg@ssec.wisc.edu), Space Science and Engineering Center, U of Wisconsin, 1225 W. Dayton St, Madison, WI 53713, United States Knuteson, R (bobk@ssec.wisc.edu), Space Science and Engineering Center, U of Wisconsin, 1225 W. Dayton St, Madison, WI 53713, United States Mlynczak, M (marty@rigel.larc.nasa.gov), NASA Langley Research Center, Langley Research Center, Langley, VA 23681, Revercomb, H (hank.revercomb@ssec.wisc.edu), Space Science and Engineering Center, U of Wisconsin, 1225 W. Dayton St, Madison, WI 53713, United States Susskind, J (Joel.Susskind-1@nasa.gov), NASA Goddard Space Flight Center, 8800 Greenbelt Road, Mail Stop 613.5, Greenbelt, MD 20771, United States Tobin, D (davet@ssec.wisc.edu), Space Science and Engineering Center, U of Wisconsin, 1225 W. Dayton St, Madison, WI 53713, United States

Knowledge of earth's outgoing longwave radiation (OLR) is an essential part of global climate change studies. A number of radiative transfer models have been developed independently for different programs. Recognizing their differences and how they compare to measurements will give us greater confidence to extend their use in models. Study of the clear sky component is the first step. Two radiative transfer model calculations of clear sky outgoing longwave radiation (OLR) are compared to the Cloud and Earth's Radiant Energy System's (CERES) measurements. For both model calculations, retrievals NASA's Atmospheric Infrared Sounder (AIRS) of surface temperature, and profiles of temperature and water vapor are used. One model, Atmospheric and Environmental Research, Inc.'s (AER) rapid radiative transfer model (RRTM), was developed to be a radiatively consistent for numerical weather models and climate change studies. The model used for the AIRS version 5 Level 2 Standard Product clear-sky outgoing longwave radiation uses the retrieved state in a rapid radiative transfer algorithm documented in Mehta and Susskind (1999) and NASA Technical Report GSFC/CR-1999-208643. The AIRS Science team plans to use an improved version of the OLR radiative transfer code in the AIRS Version 6 OLR and clear sky calculations. The Clouds and the Earth's Radiant Energy System (CERES) instrument is onboard the EOS Aqua spacecraft (along with the AIRS instrument). CERES products include both solar-reflected and Earth- emitted radiation from the top of the atmosphere (TOA) to the Earth's surface. For this study we will compare the TOA clear sky OLR from the two models globally to the CERES OLR for November 16, 2002. We also validate AIRS and CERES OLR against measurements at the ARM SGP site at Aqua overpass times between the years 2003 and 2004. Atmospheric radiosondes at the SGP site are interpolated to AIRS overpass times so that clear sky RRTM flux calculations using derived AIRS surface temperatures and emissivities would be coincident. We are able to use the AIRS high spectral observations to constrain the atmosphere state assumptions. The temperature soundings are also appended with upper level atmospheric profiles from the ECMWF model output to study their impact on TOA net flux.

A41A-0005 

Cloud Impact on Radiative Heating Rates in the Tropical Tropopause Layer Based on the CALIPSO Cloud Observations

* Yang, Q (qyang@atmos.washington.edu), Department of Atmospheric Sciences, University of Washington, 408 ATG Bldg. Box 351640, seattle, WA 98195, United States Fu, Q (qfu@atmos.washington.edu), Department of Atmospheric Sciences, University of Washington, 408 ATG Bldg. Box 351640, seattle, WA 98195, United States Hu, Y (yongxiang.hu-1@nasa.gov), NASA, Langley Research Center, Hampton, VA 23681, United States

Radiative heating rates reveal the process of the tropical upwelling in the tropical tropopause layer. In this study, we use radiative transfer calculations to derive the radiative energy budget in the tropical tropopause layer, employing balloon-borne measurements of temperature, ozone and water vapor from the SHADOZ and the cloud field retrieved from the CALIPSO cloud observations. We will focus on the impact of thin cirrus clouds on the radiative heating rates between 14 and 19 kilometers.

A41A-0006 

Evolution of the tropical atmosphere radiative budget as seen from observations and AR4 model simulations

* Andronova, N (natand@umich.edu), University of Michigan, 2455 Hayward Street, Ann Arbor, MI 48109-2143, United States Penner, J (penner@mail.umich.edu), University of Michigan, 2455 Hayward Street, Ann Arbor, MI 48109-2143, United States Xu, L (lixum@umich.edu), University of Michigan, 2455 Hayward Street, Ann Arbor, MI 48109-2143, United States

A transient change in the balance between the incoming and outgoing radiation is an important indicator of the changing Earth's climate. In this paper we use available data from satellites (1980 to present) and ground measurements (1995 to present) to reconstruct the long-term evolution of the energy budget of the tropical atmosphere (20S-20N). We compare the estimate of the radiative budget with the corresponding estimates obtained from model simulations from the AR4 database. We show that in spite of the dramatic increase in the model's ability to simulate past and recent temperature change, the models show different sensitivities to the Mt. Pinatubo eruption and do not agree with observations of the overall radiative balance tendencies over 1980-2000.

A41A-0007 

A Recipe to Include the Vertical Distribution of Radiative Forcing and Feedbacks for Climate Sensitivity Studies

* Lu, J (jlu@met.fsu.edu) Cai, M (cai@met.fsu.edu)

This paper proposes a coupled atmosphere-surface climate feedback-response analysis model (CFRAM) as a new framework for estimating climate feedback and sensitivity in coupled general circulation models with a full physical parameterization package. The formulation of the CFRAM is based on the energy balance in an atmosphere-surface column. Because the infrared radiation is the only energy flux term in the balance equation of total energy that is explicitly and directly related to temperatures in the atmosphere-surface column, the CFRAM enable us to determine the coupled atmosphere-surface temperature responses to external climate forcing and subsequent thermodynamic and dynamical feedbacks separately via a linearized infrared radiation transfer model. The decomposition of feedbacks is based on the thermodynamic and dynamical processes that directly affect vertical distribution of individual energy flux terms. Therefore, not only those feedbacks that directly affect the TOA radiative fluxes, such as water vapor, clouds, and ice-albedo feedbacks, but also those feedbacks that do not directly affect the TOA radiation, such as evaporation, convections, and horizontal heat transport, are explicitly included in the CFRAM. In the coupled atmosphere-surface CFRAM, the feedback gain matrices measure the strength of individual feedbacks. The feedback gain matrices can be estimated from the forcing inferred from individual parameterization packages and dynamical modules. The inter-model spread of a feedback gain matrix enables us to quantitatively attribute the differences of climate responses among various climate models to a specific parameterization package or dynamical module and to help us to identify the origins of the uncertainty of future climate projections in climate model simulations. The differences between the CFRAM and other feedback analysis methods, such as the TOA-based partial radiative perturbation (PRP) feedback analysis method and the online feedback suppression approach, will be illustrated using a radiative-convective model.

A41A-0008 

Effect of ancillary data on Radiation Budget at TOA and surface in ISCCP data sets

* Raschke, E A (DrRaschke@aol.com), University of Hamburg, Institute for Meteorolgy, Bundesstrasse 55, Hamburg, 20146, Germany Kinne, S (Stefan.Kinne@zmaw.de), Max Planck Institute for Meteorolgy, Bundesstrasse 55, Hamburg, 20146, Germany Zhang, Y C (yzhang@gis.nasa.gov), NASA Goddard Institute for Space Studies, Broadway, New York, NY, 10018, United States

Computations of cloud characteristics and of all radiation products from the ISCCP radiance data sets require different ancillary data, describing the state of the atmosphere and of the surface. The most important ones describe here the surface skin temperature and albedo and their temporal changes, and also the vertical structures of clouds and the atmosphere. We discovered here "trends", which are primarily caused by incorrect data handling. The final results on the vertical radiative flux divergence show an apparent trend. Thus all radiation products of the ISCCP covering now the period from mid. 1983 to the end of 2005, must be recalculated. Also the SRB products must be re-done, since they are based on the ISCCCP cloud information.

A41A-0009 

Calculating Cloud Feedbacks From Changes in Temperature Using Daily Satellite and Reanalysis Data

* Gordon, N D (ndgordon@ucsd.edu), Scripps Institution of Oceanography, University of California, San Diego, 9500 Gilman Drive Mail Code 0224, La Jolla, CA 92093-0224, United States Norris, J R (jnorris@ucsd.edu), Scripps Institution of Oceanography, University of California, San Diego, 9500 Gilman Drive Mail Code 0224, La Jolla, CA 92093-0224, United States

The representation of clouds in simulations of future climate is the largest source in uncertainty in predicting the surface temperature response to a doubling of atmospheric carbon dioxide. Since climate models do not consistently represent the sign and magnitude of cloud feedbacks on the climate system, we instead estimate these quantities from observed data. In order to do so, we must distinguish changes in cloud properties due to temperature alone from changes in cloud properties due to dynamical processes. We did this by using a k- means clustering algorithm to group midlatitude oceanic clouds with similar properties and then calculated the difference between clouds associated with warm temperatures and cold temperatures in each cluster. The warm and cold subgroups were further constrained to have similar vertical and horizontal temperature advection in order to minimize the influence of dynamics. Our analysis used daily satellite cloud data from ISCCP and dynamical information from the NCEP reanalysis. Utilizing the ISCCP flux data, we are able to calculate differences in radiative flux in the atmosphere under warmer conditions, in addition to changes to mean cloud properties. We found that cloud fraction generally decreases and cloud albedo generally increases for warmer temperature under similar dynamical conditions and vertical stratification. The reduction in cloud fraction has a bigger impact on radiation flux, suggesting that midlatitude oceanic clouds have a net positive feedback on the climate system.

A41A-0010 

A Cluster Analysis Approach to Comparing Atmospheric Radiation Measurement (ARM) Observations with General Circulation Model (GCM) Results

* Mahajan, S (salilmahajan@neo.tamu.edu), Texas A&M University, Dept. of Atmospherics Sciences, College Station, TX 77840, United States Hoffman, F M (forrest@climatemodeling.org), Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831-6016, United States Hargrove, W W (hnw@geobabble.org), USDA Forest Service, 200 WT Weaver Blvd., Asheville, NC 28804, United States Christensen, S W (swc@ornl.gov), Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831-6016, United States Mills, R T (rmills@climatemodeling.org), Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831-6016, United States

Continued validation of General Circulation Models (GCMs) is essential for their improvement, and pin-pointing their biases and systematic deviations might be of service to climate modelers. The availability of abundant multi-variate atmospheric data from the Dept. of Energy's Atmospheric Radiation Measurement (ARM) Program sites allows for comparison of atmospheric column observations to GCM simulations at high temporal resolutions at those locations. This study focuses on using a multi-variate cluster analysis approach to compare ARM observations of tropospheric vertical temperature, humidity, wind speed profiles, and surface pressure at the Southern Great Plains (SGP) site with corresponding output from an integration of the Community Climate System Model (CCSM) for the same location, highlighting observed discrepancies in the GCM results. Cluster analysis is a technique for classifying multi-variate data into distinct regimes based on Euclidean distance in phase space. A parallel clustering algorithm, designed for analyzing very large datasets, was applied to developing various atmospheric column regimes at the SGP site from the observations and, separately, from the CCSM model results. A comparison of the atmospheric regimes derived from the observations against the CCSM output proves to be useful in distinguishing their individual nature and identifying singular behavior. Some atmospheric regimes are found to be poorly represented in the CCSM. For example, while ARM SGP observations show hot humid lower tropospheric conditions are usually associated with low shear conditions, such conditions in CCSM output are associated with stronger shear. Low shear conditions in CCSM usually occur in a hot, moderately humid lower troposphere. These distinct regimes in CCSM, as compared to ARM observations, suggest misrepresentation of atmospheric states in CCSM over the SGP site, which could have ramifications on the formation of clouds in CCSM simulations, affecting the local radiation budget. In addition, the multi-variance of CCSM is lower than that of ARM observations suggesting that estimates of extremes based on GCM simulations are probably conservative.

A41A-0011 

A comparison of cloud radiative forcing as a function of climatological regime derived from A- Train data

Benson, S (sbenson@met.utah.edu), Department of Meteorology University of Utah, 135S 1460E Rm 819, Salt Lake City, UT 84112, United States * Mace, G (mace@met.utah.edu), Department of Meteorology University of Utah, 135S 1460E Rm 819, Salt Lake City, UT 84112, United States

The A-Train is providing unprecedented detail regarding the vertical distribution of cloud properties. Combining Cloudsat, Calipso, and MODIS measurements and retrievals, we are implementing a suite of cloud property retrieval algorithms to derive global cloud properties. In specific geographic regions such as the Island Continent region of the Western Pacific, the Eastern Pacific ITCZ, and the stratocumulus regimes west of subtropical Africa, South America, and North America, we are using the derived cloud properties to calculate the clear and cloudy fluxes of solar and IR radiation. Radiative closure provided by CERES as well as in situ data collected in various field programs are used as validation. From these calculations we can obtain the vertical distribution of the cloud radiative forcing. We will illustrate the role various cloud regimes play in the radiative balance of the planet by comparing the cloud radiative forcing of these regimes.

A41A-0012 

Calculation of "Validated" Radiative Heating Rates at Atmospheric Radiation Measurement (ARM) Climate Research Facilities

Mlawer, E (emlawer@aer.com), Atmospheric and Environmental Research, Inc., 131 Hartwell Ave, Lexington, MA 02421, * Delamere, J (jdelamer@aer.com), Atmospheric and Environmental Research, Inc., 131 Hartwell Ave, Lexington, MA 02421, Shippert, T (tim.shippert@pnl.gov), Pacific Northwest National Laboratory, 902 Battelle Blvd, Richland, WA 99352, Miller, M (miller@bnl.gov), Brookhaven National Laboratory, P.O. Box 5000, Upton, NY 11937, Turner, D (dturner@ssec.wisc.edu), University of Wisconsin Madison, Space Science and Engineering Center 1225 West Dayton Street, Madison, WI 53706, Jensen, M (mjensen@bnl.gov), Brookhaven National Laboratory, P.O. Box 5000, Upton, NY 11937, Johnson, K (kjohnson@bnl.gov), Brookhaven National Laboratory, P.O. Box 5000, Upton, NY 11937, Dunn, M (mdunn@bnl.gov), Brookhaven National Laboratory, P.O. Box 5000, Upton, NY 11937, Troyan, D (dtroyan@bnl.gov), Brookhaven National Laboratory, P.O. Box 5000, Upton, NY 11937, Long, C (chuck.long@pnl.gov), Pacific Northwest National Laboratory, 902 Battelle Blvd, Richland, WA 99352, Flynn, C (connor.flynn@pnl.gov), Pacific Northwest National Laboratory, 902 Battelle Blvd, Richland, WA 99352, Clough, S (sclough@aer.com), Atmospheric and Environmental Research, Inc., 131 Hartwell Ave, Lexington, MA 02421, Shupe, M (matthew.shupe@noaa.gov), University of Colorado-CIRES, NOAA/ESRL/PSD R/PSD3 325 Broadway, Boulder, CO 80305, Clothiaux, E (cloth@essc.psu.edu), Penn State, Dept. of Meteorology 603 Walker Bldg, University Park, PA 16802,

Climate and weather prediction models require accurate calculations of vertical profiles of radiative heating. In contrast to calculations of radiance and irradiance at the surface and top-of-atmosphere (TOA), heating rate calculations cannot be directly validated due to the lack of corresponding observations. However, surface and TOA measurements can indirectly establish the quality of computed heating rates through validation of the calculated irradiances at the atmospheric boundaries. The Atmospheric Radiation Measurement (ARM) program has produced continuous profiles of computed radiative heating rates at its Climate Research Facilities that have been validated using this approach. The computed surface and TOA irradiances have been subject to extensive radiative closure analysis, an effort that has led to significant advancements in the three components of radiative closure studies: model calculations, including spectroscopic parameters; radiometric measurement accuracy; and the specification of the atmospheric state in the radiating column. In particular, this effort has taken advantage of ARM's substantial set of active and passive sensors that are sensitive to the cloud properties within the radiating column to evaluate numerous cloud property retrieval algorithms. This effort, named the ARM Broadband Heating Rate Profile (BBHRP) project, is a collaboration of all the working groups in the program. This presentation will present selected results from this closure study for both clear and cloudy conditions, including an analysis of the relative model-measurement agreement resulting from the use of various cloud property retrieval algorithms. Focus will be placed on results from the ARM North Slope of Alaska site, including the presentation of computed heating rates for cases of interest. http://engineering.arm.gov/~shippert/BBHRP/

A41A-0013 

Vertical profiles of aerosol extinction and radiative heating at Niamey, Niger

* McFarlane, S (sally.mcfarlane@pnl.gov), Pacific Northwest National Laboratory, P.O. Box 999 MSIN K9-24, Richland, WA 99352, Kassianov, E (evgueni.kassianov@pnl.gov), Pacific Northwest National Laboratory, P.O. Box 999 MSIN K9-24, Richland, WA 99352, Flynn, C (connor.flynn@Pnl.gov), Pacific Northwest National Laboratory, P.O. Box 999 MSIN K9-24, Richland, WA 99352, Barnard, J (jim.barnard@pnl.gov), Pacific Northwest National Laboratory, P.O. Box 999 MSIN K9-24, Richland, WA 99352,

Land use and land cover changes may lead to increases in Saharan dust outbreaks and increased dust aerosol loading in the atmosphere. It is important to understand the impact of Saharan dust on the Earth's radiation budget in order to improve model simulations of regional and global climate. Details of the radiative impact depend on the amount, vertical profile, and optical properties of the observed aerosol. The ARM Mobile Facility (AMF) was deployed in Niamey, Niger during 2006 as part of the RADAGAST project (Radiative Atmospheric Divergence using ARM Mobile Facility, GERB data and AMMA Stations) in cooperation with the African Monsoon Multidisciplinary Analysis (AMMA) experiment. This deployment represents the first long- term series of measurements of aerosol properties from the surface in the Sahel region and provides an unprecedented opportunity to examine the radiative heating profiles associated with aerosol in this region. Using aerosol optical properties derived from the Multi-Filter Rotating Shadowband Radiometer (MFRSR) and the Atmospheric Emitted Radiance Interferometer (AERI), profiles of relative aerosol extinction from the micropulse lidar (MPL), and measurements of broadband surface radiation at the AMF site, we examine the vertical profile of aerosol extinction and aerosol radiative heating during the dry season (January - March and Oct-Dec, 2006) at Niamey.

A41A-0014 

Using CALIPSO Space Lidar Data in Conjunction with Passive Remote Sensing for Characterization of Spatiotemporal Distribution of Asian Dust Outbreaks and Their Radiative Impact

* Choi, H (hyung-jin.choi@eas.gatech.edu), School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, 30332, Sokolik, I N (irina.sokolik@eas.gatech.edu), School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, 30332, Winker, D M (david.m.winker@nasa.gov), NASA Langley Research Center, MS/435, Hampton, VA 23681,

A better understanding of the properties and spatiotemporal distribution of atmospheric dust is needed for improved predictions of aerosol radiative forcing on climate. We use CALIPSO data in conjunction with A-Train satellite multi-sensor observations (Ozone Monitoring Instrument, OMI, Moderate-Resolution Imaging Spectroradiometer, MODIS, and CloudSat) as well as ground-based data to investigate the dynamics of East Asian dust plumes during March-April of 2007, considering dust sources and mid- and long-range transport. In addition, using recent data on the composition of Asian dust, we compute the dust optical properties (lidar ratio, particle depolarization ratio and color ratio) to aid in interpretation of CALIPSO data. Based on CALIPSO and CloudSat observations, we investigate the importance of the layered vertical distribution of dust and clouds on the dust radiative impact. The effect of ageing of dust and its mixing with other aerosol is also examined. The results of intensive one-dimensional radiative transfer simulations addressing these issues will be presented with the focus on TOA radiative forcing and heating/cooling rates in differing dust-laden conditions.

A41A-0015 

Preliminary Study On Surface Radiation Characteristic Over Semi-Arid Region Of Loess Plateau

Bi, J (bijr997@yahoo.com) * Huang, J (hjp@lzu.edu.cn) Liu, Y (liuyzh@lzu.edu.cn) Shi, J (shijs06@lzu.cn) Huang, Z (huangzhw03@lzu.cn) Zhang, W (wzhang@lzu.edu.cn)

By using the land-surface radiative data observed over Semi-Arid Climate and Environment Observatory of Lanzhou University during April 12, 2006 to June 30, 2007, the variational rule of land-surface radiation over Semi- Arid region of Loess Plateau is preliminarily analyzed, and the monthly averages of surface radiation balance, surface albedo and influence mechanism are completely studied. The result shows that the annual averaged radiant intensity is comparatively strong in this region. In the influence of land-surface conditions and synoptic conditions, the monthly averages of surface radiation take on irregular or territorial characteristic. Atmosphere and land-surface need about two months to response to the heat of radiation in the variation of annually mean radiation, and need about two hours and one hour to response to the heat of radiation in diurnal variation, respectively. The all-year variational range of atmosphere and land-surface radiations in semi-arid region are 162.6 and 180.4180.4, respectively, which are much smaller than that in arid of deserted region (about 100%). In other words, it means that the annual averaged cloud in semi-arid region is much more than in arid region, and atmosphere and soil intensively mitigate the variability of surface radiation in semi-arid region. The Annual average of surface albedo in semi-arid region of Loess Plateau is 0.2432, which is smaller than that in arid region (about 0.259), and greater than that in Dingxi Site(about 0.20). And the big values of surface albedo consist with the appearance of droughty weather and snowfall synoptic, whereas the small values of surface albedo correspond to the emergence of cloudy sky and rainfall synoptic. http://climate.lzu.edu.cn/~jhuang/

A41A-0016 

Assessing Changes in Surface Fluxes over Land due to Linked Changes in Aerosol and Clouds

* Berg, L K (larry.berg@pnl.gov), Pacific Northwest National Laboratory, PO Box 999, Richland, WA 99352, United States Kassianov, E (Evgueni.Kassianov@pnl.gov), Pacific Northwest National Laboratory, PO Box 999, Richland, WA 99352, United States Flynn, C (connor.flynn@pnl.gov), Pacific Northwest National Laboratory, PO Box 999, Richland, WA 99352, United States McFarlane, S (sally.mcfarlane@pnl.gov), Pacific Northwest National Laboratory, PO Box 999, Richland, WA 99352, United States

Recent large-eddy simulation studies have examined the response of warm continental cumulus clouds to aerosol loading and have demonstrated that aerosol radiative effects can significantly reduce surface fluxes, and thus decrease convection and the cloud fraction. Both aerosol and clouds affect the surface fluxes, making it difficult to predict different and possibly compensating changes in the surface energy balance. To estimate the sensitivity of the surface fluxes to changes of aerosol and cloud properties, we use collocated and coincident ground-based measurements and Terra/Aqua satellite observations at the Atmospheric Radiation Measurement (ARM) Climate Research Facility (ACRF) Southern Great Plains (SGP) site. We estimate this sensitivity in a specific 5-summer dataset of fair-weather cumulus (FWC) clouds and mostly non-absorbing aerosols that occur at the ACRF SGP site. In particular, we demonstrate that the sensitivity depends on both the time of day and the cloud size. Since the SGP-obtained statistics appear to be fairly typical of the mid-latitude regions, we expect that our findings may be valid for a range of continental FWC clouds and aerosols.

A41A-0017 

Surface Radiative Forcing by Clouds and Diamond Dust Measured During Winter 2006-2007 at Eureka, Canada

* Lesins, G (glen.lesins@dal.ca), Dalhousie University Department of Physics and Atmospheric Science, Dunn Building, Halifax, NS B3H 1Z9, Canada Bourdages, L (line.bourdages@gmail.com), Dalhousie University Department of Physics and Atmospheric Science, Dunn Building, Halifax, NS B3H 1Z9, Canada Duck, T (tom.duck@dal.ca), Dalhousie University Department of Physics and Atmospheric Science, Dunn Building, Halifax, NS B3H 1Z9, Canada Eloranta, E W (eloranta@lidar.ssec.wisc.edu.), University of Wisconsin Space Science and Engineering Center, 1225 W. Dayton St., Madison, WI 53706, United States Walden, V P (vonw@uidaho.edu), University of Idaho Department of Geography, PO Box 443021 McClure 305A, Moscow, ID 83844-3021, United States

During the Arctic winter, in the absence of sunlight, most cloud and diamond dust layers exert a positive (warming) radiative forcing at the ground by blocking the longwave infrared window and thus help to prevent surface temperatures from dropping to even lower values. As part of the Canadian Network for the Detection of Atmospheric Change (CANDAC) and the NOAA Study of Environmental Arctic Change (SEARCH), surface based remote sensing measurements are being taken of the cloud properties and the radiative forcing at Eureka (80N, 86W) in the Nunavut Territory in the Canadian High Arctic. Here we present results obtained during the winter of 2006-2007 using the University of Wisconsin Arctic High Spectral Resolution Lidar (AHSRL) and Polar Atmospheric Emitted Radiance Interferometer (P-AERI) demonstrating the importance of cloud radiative forcing. Even under clear sky conditions the measured diamond dust surface infrared downward radiative forcing ranged from 7 to 32 W/m2 in the wavelength band from 4 to 20 microns for visible optical depths ranging from 0.23 to 1.7. Lidar extinction and depolarization ratios showed that these events are dominated by ice crystals. This is an important difference for earlier studies at other Arctic locations which concluded that significant radiative forcing from diamond dust occurred only if liquid water clouds were also present. At Eureka the diamond dust events can produce high enough optical depths even in the absence of liquid water. In addition there are events where a thin layer of supercooled cloud water caps a layer of ice crystals which extends to the surface. The differences in the radiative forcing of these events will also be examined. These results have important implications for atmospheric processes in the winter Arctic including Arctic smog, dehydration effect, minimum attainable temperature, surface energy balance and regional climate change.

A41A-0018 

Effects of Cloudiness on the Daily and Annual Radiation Balance: Elaboration on the Shartwave and Longwave Radiation

* Malek, E (emalek@mendel.usu.edu), Utah State University, 4820 Old Main Hill, Logan, Uta 84322-4820, United States

Clouds are visible masses of condensed droplets and frozen crystals of water in the atmosphere above the Earth. They make changes in the energy balance at local, regional, and planetary scales. They affect the climate by positive and negative feedback. To study these effects at local scale, we set up a radiation station which uses two CM21 Kipp & Zonen pyranometers (one inverted), and two CG1 Kipp & Zonen pyrgeometers (one inverted) in a semi-arid mountainous valley in Logan, Utah, U.S.A. The pyranometers and pyrgeometers were ventilated using four CV2 Kipp & Zonen ventilation systems. Ventilation of pyranometers and pyrgeometers prevents dew and frost and snow accumulation which otherwise would disturb the measurement. All sensors were installed at about 3 m above the ground, which is covered with natural vegetation during the growing season (May - September). The incoming (Rsi) and outgoing (Rso) solar or shortwave radiation, the incoming (Rli, atmospheric) and outgoing (Rlo, terrestrial) longwave radiation, along with the 2-m air temperature, humidity, and pressure have been continuously measured since 1995. We also measured the 3-m wind speed and direction, the surface temperature (using an IR thermometer) and precipitation (using a heated rain gauge). These parameters have been measured every 2 seconds and averaged into 20 minutes. For this study we chose three days: 6 April (a partially cloudy day), 29 July (a cloudless day), and 29 November (an overcast day), 2005, along with continuous study throughout the year 2005. We developed an algorithm for evaluation of cloudless-sky incoming (atmospheric) longwave radiation. Equations for cloudless-sky incoming shortwave and atmospheric longwave radiation were applied to compare the cloud-free measurements with the actual ones. Cloudless – measured incoming shortwave (solar) radiation is an indication of how much less radiation was received due to cloudiness (if any). Measured – cloudless incoming longwave (atmospheric) radiation shows the cloud (if any) contribution to the radiation budget. The results indicate that for the partial cloudy day of 6 April, 2005, cloudiness caused less shortwave radiation 23.29 – 13.76 = 9.53 MJ m-2 d-1 received at the surface. On the same day cloud contributed an additional radiation of 25.44 – 23.44 = 2.00 MJ m-2 d-1. On 29 November, 2005, these values were 9.37 – 1.98 = 7.39 and 28.82 – 23.86 = 4.96 MJ m-2 d-1, respectively. On the annual basis, the 2005 cloudiness caused a reduction of 7279 – 5800 = 1479 MJ m-2 y-1 for the shortwave radiation, while the additional longwave radiation due to cloudiness amounted to 9976 – 9573 = 403 MJ m-2 y-1. The cloudiness in 2005 caused a negative feedback on the climate in this valley.

A41A-0019 

Radiative Forcing at the Surface by Clouds, Aerosols, and Water Vapor Over Tropical Oceans

* Key, E (Erica.Key@cetp.ipsl.fr), CETP, IPSL, 10/12 Avenue de l'Europe, Velizy-Villacoublay, 78140, France Minnett, P (pminnett@rsmas.miami.edu), University of Miami, RSMAS, 4600 Rickenbacker Causeway, Miami, FL 33149, United States Szczodrak, G (gszczodrak@rsmas.miami.edu), University of Miami, RSMAS, 4600 Rickenbacker Causeway, Miami, FL 33149, United States Caniaux, G (guy.caniaux@meteo.fr), CNRM, Meteo-France, 42 Avenue Gustave Coriolis, Toulouse, 31057, France Voss, K (voss@physics.miami.edu), University of Miami, Physics Department, Miami, FL 33124, United States Bourras, D (Denis.Bourras@cetp.ipsl.fr), CETP, IPSL, 10/12 Avenue de l'Europe, Velizy-Villacoublay, 78140, France

Data from recent campaigns conducted in the tropical Atlantic and Indian Oceans provide thorough testbeds for determining the contribution of clouds, aerosols, and water vapor to surface radiative forcing, with particular focus on areas of extreme SST gradients. Oceanographic cruises conducted during the African Monsoon Multidisciplinary Analysis included sampling monsoon onset in the Gulf of Guinea, which was characterized nearshore by rain and haze, the latter being a combination of water vapor and continental and pollution aerosols. Offshore and nearer to the equatorial cold tongue, the ITCZ was the dominant northern hemisphere cloud feature, while drier, cooler air masses existed south of the equator. The R/V Ronald H. Brown, operating a north-south transect along 23 W, encountered both atmospheric tropical wave conditions as well as dry Saharan Air Layers. In the Indian Ocean, the N/O Le Suroit occupied a point station near a positive SST anomaly to observe the onset of convection associated with the MJO and strong diurnal warming signatures. Combining radiative and turbulent flux data with measured and modeled profiles of the marine and atmospheric boundary layer, the evolution and interaction of the total air-sea column is observed. Particular emphasis is placed on the radiative forcing of clouds, aerosols, and water vapor on the sea surface skin temperature, towards the improvement of current diurnal warming models, which simplify atmospheric radiative effects into a general cloud parameter.

A41A-0020 

Cloud and Aerosol Measurements at the Clouds and the Earth's Radiant Energy System (CERES) Ocean Validation Experiment (COVE)

* Fabbri, B (Bryan.E.Fabbri@nasa.gov), Science Systems and Applications, Inc. (SSAI), One Enterprise Parkway Suite 200, Hampton, VA 23666, United States Schuster, G (Gregory.L.Schuster@nasa.gov), NASA Langley Research Center, Science Directorate Mail Stop 420 Building 1250, Rm. 165, Hampton, VA 23681, United States Rutledge, K (Charles.K.Rutledge@nasa.gov), Science Systems and Applications, Inc. (SSAI), One Enterprise Parkway Suite 200, Hampton, VA 23666, United States Denn, F (Frederick.M.Denn@nasa.gov), Science Systems and Applications, Inc. (SSAI), One Enterprise Parkway Suite 200, Hampton, VA 23666, United States Madigan, J (James.J.Madigan@nasa.gov), Science Systems and Applications, Inc. (SSAI), One Enterprise Parkway Suite 200, Hampton, VA 23666, United States

The CERES Ocean Validation Experiment (COVE) is located 25 km off the coast of Virginia Beach, Virginia and has been a part of many studies and projects. We focus here on some of the most recent measurements and analysis conducted at this site. The relationship between aerosol inversions with cloud fraction and relative humidity will be presented. Using AERONET data for aerosol inversions and Long-Ackerman for cloud fraction, it will be shown that cloud fraction correlates better than relative humidity versus aerosol inversion except in the course volume, although relative humidity demonstrate good relationships as well. Angstrom Exponent (AE 500-870) and Aerosol Optical Thickness (AOT 500) with cloud fraction will also show similar results bearing strong relationships. Cloud conditions play an important role on insolation. Cloud fraction was used to infer the percentage of the sky covered by clouds (clear, partly cloudy or overcast) at the COVE site. Being a warm, humid site in the summer, the annual trend will be discussed where the summer months tend to be the least clear while the fall months being the most clear. Derived Micro-Pulse Lidar (MPL) lowest cloud base height data and statistics will also be shown. Aerosol climatology at this location indicate AOT's and AE's that are consistent with polluted urban aerosols, which is not surprising given the predominantly westerly winds passing over Virginia Beach and Norfolk, VA. Although this is the case, there is a small percentage of clean maritime air indicating that coarse mode aerosols also influence the COVE site. Back trajectories and Angstrom exponent data will be discussed to show this influence.

A41A-0021 

New Insights Into the Column Radiative Budget Using Ground Based Hyperspectral Zenith Radiance Measurements

* McBride, P (mcbridep@colorado.edu), University of Colorado, Laboratory for Atmospheric and Space Physics Campus Box 392, Boulder, CO 80309, United States Pilewskie, P (peter.pilewskie@lasp.colorado.edu), University of Colorado, Laboratory for Atmospheric and Space Physics Campus Box 392, Boulder, CO 80309, United States Schmidt, S (sebastian.schmidt@lasp.colorado.edu), University of Colorado, Laboratory for Atmospheric and Space Physics Campus Box 392, Boulder, CO 80309, United States Coddington, O (Odele.Coddington@lasp.colorado.edu), University of Colorado, Laboratory for Atmospheric and Space Physics Campus Box 392, Boulder, CO 80309, United States

For the past 18 months a new instrument (Shortwave Spectrometer, SWS) has been used to continuously monitor the spectrally resolved zenith radiance at the DOE ARM Southern Great Plains (SGP) Climate Research Facility. The primary objective behind its deployment was to enhance cloud remote sensing capabilities at SGP, in particular the retrieval of cloud optical thickness and, in unison with other observations, cloud water path. However, some of the most intriguing observations have occurred under cloud-free conditions. Zenith radiance is a relatively unexplored variable for deriving aerosol properties yet it is far more sensitive to small changes in aerosol burden and angular scattering patterns than either the directly transmitted irradiance or global irradiance. We present new methods for quantifying the column radiative energy budget through the analysis of zenith spectral radiance and aerosol and cloud remote sensing.

Author(s) (2007), Title, Eos Trans. AGU, 88(52), Fall Meet. Suppl., Abstract #####-##.