A23A-01
Detecting Climate Change in the Great Lakes
The Great Lakes hold specific significance to the economy and ecology of the eight states it unites. For this
project, using the 25-year long record of meteorological data from NOAA's National Buoy Data Center (NDBC) for
ice-free conditions, it can be shown that despite large variability, climate change effects on the Great Lakes region
can be detected. This was achieved by: (1) compiling mean monthly values from raw hourly data from the NOAA
NDBC for period 2002-2005 which had not been done yet; (2) statistically analyzing monthly data for period 1980-
2005; and (3) comparing our results to other climate indicators related to events such as ENSO (El-Nino
Southern Oscillation), PNA (Northern American Pattern), and NAO (North Atlantic Oscillation). Preliminary findings
for the considered period indicated an increase in the temperature median of 2°C; a decrease in the high
extreme of pressure correlating to an increase in the high extreme of wind velocity. Additionally, in dependence on
the buoy location, we observed two to four-year cycle in the summer mean lake temperature values.
Understanding and attributing such climate behavior in the Great Lakes can help in both adjusting economically
to probable changes, as well as understanding global climate changes.
A23A-02
How do Cyclones Spin up? Hurricane Dennis as a Case Study.
Application of the flux form of the vorticity equation shows that a cyclone will develop when the tendency of convergence to enhance the low-level circulation of a system is greater than the tendency of surface friction to spin the system down. In the present work we study the developing stages of Hurricane Dennis by applying this form of the vorticity equation. We use dropsonde data released from the two NOAA P-3 aircraft in July of 2005 as part of the IFEX (Intensity Forecasting EXperiment) campaign. We find the convergence of absolute vorticity into the system directly from the dropsonde data. Then we find the spin-down tendency due to frictional forces by making the assumption that the surface stress is distributed uniformly through the depth of the inflow layer, taken to be the 100mb layer closest to the surface. These calculations enable us to evaluate the spin-up rate of the system. Our results show a negative tendency in the development of the cyclone which implies that it should not have spun up. Nevertheless, we know the system evolved into a hurricane. This supports earlier results obtained in TEXMEX (Tropical EXperiment in MEXico). We will discuss the possible causes of this discrepancy. The most likely cause is that the eddy transport of momentum is more complex than we have envisioned here.
A23A-03
Observed Theoretical Upper Atmospheric Temperature Comparisons From SABER and WACCM
Observed upper atmospheric temperatures from the NASA SABER sensor and the NCAR WACCM theoretical model were made within the years 2002 to 2007. These upper atmospheric measurements come from the temperature data set derived using measurements from the CO2 channels aboard the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument. This sensor is part of the NASA Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite which has been operational since January 2002. Five years of data are used to identify global trends from and make comparisons with the Whole Atmosphere Community Climate Model (WACCM). Seasonal comparisons are made for atmospheric pressures between 10 and 10-4 millibars, and over a global range of latitudes and longitudes. These results are used to examine the long term trends of the temperature during a portion of a solar cycle, and help ascertain what factors affect the temperature trends. The F10.7 index will be used to enable correlations to be obtained.
A23A-04
New criterion to select the South Atlantic Convergence Zone
The South Atlantic Convergence Zone (SACZ) is a climatic aspect of the intraseasonal scale that produces intense precipitation in Southeast Brazil during summer Austral. The SACZ is characterized for a high variability convective region located in eastern Cordilheiras of the Andes with northeast-southeast orientation. In addition extend Southeast Amazon until South Atlantic (Zhou and Lau 1998; Liebmann et al, 1999; Carvalho et al, 2004). The many works that studied SACZ (Carvalho, Jones e Liebmann, 2004; Jones et al, 2004, for example) long wave radiation (ROL), is used which proxy of precipitation. In the first moment, it describes the position of event; however the precipitation is more adequate, principally in the used data series obtain of the climatic models. A study of the characterization of the South Atlantic Convergence Zone (SACZ) is presented. It was determined 48 events of ZCAS between 1995 to 2005 during the November to March period. Based on rainfall data, a new criterion was defined in order to select the SACZ events and their results were compared with the previous events. The results indicated that the new criterion did a good job in representing the SACZ. For this reason, um test with climatic model data series (REGCM3 Model, Giorgi et al., 1993) is presented.
A23A-05
Influence of the Inter-ENSO Extremes on the South American Moisture Transport during opposite PDO Phases
The impact of the inter El Niño/Southern Oscillation (ENSO) variability on the atmospheric circulation and the moisture distribution over the South America according to the Pacific Decadal Oscillation (PDO) phases is investigated. Emphasis is done on the spring and austral summer. It was found that during the summer when weak El Niños (EN) and neutral ENSO events occur during cold PDO regime the moisture transport from the tropics to the subtropics, particularly around the South Atlantic Convergence Zone region, seems to be more important than in the warm PDO phase. When strong EN is in phase with warm PDO the feedback between them seems to favor an enhanced meridional moisture transport from tropical latitudes to the La Plata Basin. Substantial differences among the austral seasons have been found on the composites of the circulation anomalies for the extreme ENSO events that occur during warm PDO. These differences are more conspicuous when the atmosphere is influenced by the warm phase of the ENSO. In subtropical latitudes around the La Plata Basin region, the most significant difference from spring to the summer season during strong EN events is the increase on the intensity of the circulation anomalies over that region. On the other hand, during weak EN and La Niñas events circulation patterns from one season to another can have opposite signals in the same region. It is demonstrated that the intensity of an ENSO episode can modulate the moisture transport in the South American continent. This study contributes to the current knowledge about the South America circulation anomalies associated with the interannual variability taking into account the PDO phases. Some more detailed analysis and numerical experiments are currently been carried out and will be presented elsewhere.
A23A-06
Coherence Between Periodicities of Atmospheric Teleconnection Patterns and Quasi- periodic Atmospheric and Extra-terrestrial Phenomena
We apply wavelet analysis to modes of low-frequency atmospheric circulation variability (teleconnection patterns). The modes are defined by rotated principal component analysis of monthly or 10-day mean 500 hPa heights in the Northern Hemisphere north of 20°N over 1950-2003. The uneven distribution of variance during the annual cycle is compensated for by weighting by its monthly (10-day) mean standard deviation. 13 modes are detected, most of which are active in winter. Morlet wavelet is selected as a basis for the wavelet transform. The main feature of wavelet spectra of the variability modes is their intermittency: generally, no period (within the range between 1 and 15 years) appears as dominant throughout the whole analyzed time domain. There are only a few exceptions, which have undergone stationary oscillations; e.g., 9 years for the North Atlantic Oscillation and 14 years for the Tropical / Northern Hemisphere pattern. The effects of the sampling interval (monthly or 10 day means) and of the way of compensation for the annual cycle of variability are marginal. We also calculate coherence between the wavelet spectra of the modes and those of quasi-periodic phenomena such as quasi- biennial oscillation, El Niño - Southern Oscillation, and 11-year solar cycle. Its statistical significance is determined by the Monte Carlo test. The statistically significant coherence appears, for example, between several variability modes, including the North Atlantic Oscillation, and solar activity for periods of 8 to 9 years.
A23A-07
Estimating the fractal dimension of the atmosphere and the predictability via Lyapunov exponents for the Caribbean region
The fractal dimension, Lyapunov-exponent spectrum, and predictability are analyzed for chaotic attractors in the atmosphere by analyzing the time series of daily wind speeds over the Caribbean region. It can be shown that this dimension is greater than 8. However, the number of data points may be too small to obtain a reliable estimate of the Grassberger-Procaccia (1983a) correlation dimension because of the limitations discussed by Ruelle (1990). These results lead us to claim that there probably exist no low-dimensional strange attractors in the atmosphere. Because the fractal dimension has not yet been saturated, the Kolmogorov entropy and the error-doubling time obtained by the method of Grassberger and Procaccia (1983b) are sensitive to the selection of the time delay and are thus unreliable. A practical and more reliable method for estimating the Kolmogorov entropy and error-doubling time involves the computation of the Lyapunov-exponent spectrum using the algorithm of Zeng et al. (1991). Using this method, it is found that the error-doubling time is 2-3 days for time series over the Caribbean region. This is comparable to the predictability time found by Waelbrock (1995) for a single station in Mexico. The predictability time over land is slightly less than that over ocean which tends to have higher climatic signal-to-noise ratio. This analysis impacts on the selection of prediction tools (deterministic chaotic linear and non-linear maps or linear stochastic modeling) for wind speeds in the short term for wind energy farm resource planning and management. We conclude that short term wind predictions in the Caribbean region, for a few days ahead, may be best done with a stochastic model instead of a deterministic chaotic model. References Grassberger, P., and I. Procaccia. 1983a. Measuring the strangeness of attractors. Physica D 9: 189-208. Grassberger, P., and I. Procaccia. 1983b. Estimating the Kolmogorov entropy from a chaotic signal. Phys. Rev. A. 28: 2591-2593. Ruelle, D. 1990. Deterministic chaos: the science and the fiction. Proc. Royal Soc. Lond. A 427: 241-248. Waelbrock, H. 1995. Deterministic chaos in tropical atmospheric dynamics. J. Atmos. Sci. 52: 2404-2415. Zeng, X., R. Eykholt, and R. A. Pielke. 1991. Estimating the Lyapunov-exponent spectrum from short time series of low precision. Phys. Rev. Lett. 66: 3229-3232.
A23A-08
Evaluation of soil moisture in the Florida State University climate model-National Center for Atmospheric Research community land model (FSU-CLM) using two reanalyses (R2 and ERA40) and in situ observations
The simulated soil moisture from the Florida State University/Center of Ocean and Atmosphere Prediction
Studies (FSU/COAPS) global spectral model coupled to the National Center for Atmospheric Research
community land model (CLM2) is evaluated using two reanalyses (the European Centre for Medium-Range
Weather Forecasts 40-year Reanalysis (ERA40) and the National Centers for Environmental
Prediction/Department of Energy Reanalysis 2 (R2)) and in situ observations in Illinois and China from the Global
Soil Moisture Data Bank. While the soil moisture was prescribed in the previous FSU/COAPS model, the
implementation of the CLM2 within the FSU/COAPS (hereafter FSU-CLM) provides a prognostic soil moisture
(both soil liquid water and soil ice) in 10 vertical layers. For the first layer (0-10 cm) the comparison of the soil
moisture annual cycle between the FSU-CLM and the two reanalyses shows that in the Northern Hemisphere
(NH) the FSU-CLM and the ERA40 are in phase but they are out of phase with the R2. While a parameterization of
the soil ice process is included in both the FSU-CLM and ERA40, it is not included in the R2. In this study, we
found that the soil ice plays a key role in determining the soil moisture variation over the NH. The two reanalyses
and the FSU-CLM are also compared with in situ observations. The FSU-CLM turns out to follow the annual cycle
of the in situ observations better than both reanalyses.
http:www.coaps.fsu.edu/~marie
A23A-09
Analysis of the Spatio-temporal Distribution of Latent Heating in the Southeast Asian Monsoon Region
The latent heat released as a result of deep convection plays an important role driving the global atmospheric circulation, including the Southeast Asian Monsoon. In particular, knowing the spatio-temporal structure of the latent heating during the wet monsoon season its very important to understand the interaction between the seasonal features of the monsoon and the summer manifestation of the intraseasonal oscillation in the Indian Ocean basin, and hence the distribution of the precipitation during the wet season.. For this reason, TRMM TMI data (1B11 and 2A12 algorithms) from May to September of different years is used to estimate the distribution of the latent heating in the vertical during active and break conditions as defined by the intraseasonal oscillation. This analysis is performed both for the entire region including areas with and without storms, as well as only for regions with storms. These storms were classified using a clustering algorithm based on thresholds of Brightness Temperature. A comparison of the average vertical heating profiles for storms with and without Mesoscale Convective Systems (MCSs) is performed. Similarly, a detailed spatial analysis focusing in key regions of the Southeast Asian monsoon, including Bay of Bengal, Equatorial Indian Ocean, Central India and Western Ghats was carried out. Modulation of the latent heating due to Intraseasonal variability is also studied, focusing on the differences between the latent heating profiles during the suppressed and active phases of the oscillation. Preliminary results show significant differences in the vertical distribution of the heating between storms with and without MCSs as well as for different regions and different phases of the intraseasonal oscillation. For highly developed convective storms (MCS) it was noted a deep warming aloft stronger than for those in early stages of development. Regional profiles of latent heating show differences in the vertical distribution related to the origin of the precipitating cloud inside each region.
A23A-10
Simulation of a Coupled Mechanism for Local Intraseasonal Variability in the Tropics
During the transition phase between suppressed and active phases of the tropical intraseasonal oscillation (ISO) the atmosphere and ocean undergo important changes. Positive SST anomalies cause changes in atmospheric boundary layer temperature creating anomalous surface pressure gradients, winds and low level mass convergence which may lead to convection. Surface winds are strengthened and exert stress over warmer than average surface oceanic waters, leading to enhanced evaporation, and low-level atmospheric moistening which preconditions the atmosphere for deep convection. The cloudiness associated with the active convection acts to cool the surface of the ocean. With the reduction of SST the active phase ends. This local oscillation will then project onto the zonal circulation resulting in the eastward propagation of the convective anomalies. According to the previous mechanism, the time needed to elevate the SST by enhanced downward solar radiation during the suppressed phase as well as the time needed to destabilize the lower troposphere due to the higher SST determines the local timescale of the ISO. This implies that dynamics of the oceanic mixed layer is also very important for the ISO timescale. In this study we explore the role of local ocean-atmosphere coupling in generating intraseasonal variability, and specifically, the role of the oceanic mixed layer dynamics in determining the time-scale of the resulting oscillation. In particular, we study the mechanism previously described by using two different one-dimensional coupled models. In both setups, the ocean component is the Kantha-Clayson ocean mixed layer. In the first case, the atmospheric component is an empirical scheme designed based on TOGA/COARE observations. In this scheme, the rate of change of different atmospheric variables such as surface wind, specific humidity, outgoing longwave radiation, among others are statistically related to changes in SST. In this manner, SST controls the atmosphere which then drives changes in SST, allowing the reproduction and detailed study of the observed coupling mechanism. In the second set-up, the atmospheric component of the couple system corresponds to the single column model version of the NCAR CCM. In this framework, the evolution of the transition period is studied under different ocean-atmosphere configurations to determine the degree of local coupling associated to ISO events.
A23A-11
Development of a new Method for Determination of Atmospheric Halogen Atom Concentrations
A flowtube reactor has been developed for the quantitative determination of atmospheric halogen atom concentrations. The technique operates by drawing atmospheric halogen atoms (Cl, Br, I) into a 20 mm diameter quartz flowtube, in which they quickly react with an introduced alkene (trifluoropropene) and NO to produce a halogenated ketone that is detected by gas chromatography with electron capture detection (GC-ECD). This method allows for the "direct" determination of atmospheric halogen atom concentrations, which have so far only been determined by indirect methods, e.g. as inferred from hydrocarbon decay rates. The fluorinated alkene reagent is utilized to increase the final product's ECD sensitivity as well as provide a compound not found in the environment (i.e. very low blanks), leading to greater overall instrument sensitivity. A solid-sorbent sample preconcentrator is used following reaction in the flow tube to increase the sample volume and allow detection of the halogenated ketone product at concentrations in the ppq and ppt range. The halogen monoxide radicals (XO) can also be determined by conversion to X via reaction with NO at the inlet. The resulting halogen atom concentration measurements allow for the greater understanding of halogen atom photochemistry in the lower troposphere. Here we show results from laboratory tests and system calibrations.
A23A-12
Variability of Particle Number Concentration and Size Distribution in Barcelona
Particle number concentrations and size distributions of aerosols between 13-800 nm were determined at an urban background location in Barcelona, Spain, from November 2003 to December 2004. Mean levels of particle number in this range were around 17.000 cm-3, being the most of them ultrafine particles (<100 nm). The peak of the distribution was found at around 40 nm. High number concentrations were obtained during wintertime, due to lower dispersive conditions, while low number concentrations were found in April and August, related with Atlantic advections and fewer emissions, respectively. This study demonstrate that road traffic is the most contributor to particle number levels, whereas the atmospheric processes play an important role on the evolution of these levels.
A23A-13
Characterization of a Dilution Modulation CIMS-Based Method for Measuring Tropospheric Peroxy Radical Concentrations
Over the past few years, we have developed an improved method for quantification of peroxy radicals (HO2 and HO2+RO2) using chemical ionization mass spectrometric detection, compared to our previous method (Edwards et al., 2003). This method was employed recently during the MIRAGE and INTEX-B campaigns in spring 2006. Our method involves operating the instrument inlet at two specific ratios of NO to O2. At low [NO]/[O2], HO2 plus most RO2 radicals are measured with high efficiency, while at high [NO]/[O2], HO2 is measured, but most RO2 radicals are measured with low efficiency. This is due to the competition for reaction of alkoxy radicals (RO, produced when RO2 radicals react with NO) between O2 (usually to produce HO2) and NO (to produce alkyl nitrites). We vary the [NO]/[O2] ratio by diluting ambient air by half with either oxygen or nitrogen about, while at the same time changing reagent NO and SO2 concentrations by a factor of ten. During our laboratory investigations, we examined the behavior of the instrument over a wide range of [NO]/[O2] ratios. We have quantified the response to RO2 radicals derived by reacting OH with various precursor hydrocarbons (methane, alkanes, alkenes, halocarbons, alcohols, aromatics and oxygenated species). The inlet chemistry converts ambient peroxy radicals to gas-phase sulfuric acid. We ionize the sulfuric acid by reaction with negatively charged nitrate reagent ions leading to production of bisulfate ions. We measure the abundances of reagent and product ions with mass spectrometry using quadrupole mass filtering and ion counting. Here, we described the results of the laboratory experiments we performed to characterize the behavior of the instrument. This characterization has led to detailed understanding that allows hydroperoxy and organic peroxy radical concentrations to be quantified aboard aircraft and on ground-based platforms. Edwards, G. D., C. A. Cantrell, S. Stephens, B. Hill, O. Goyea, R. E. Shetter, R. L. Mauldin, E. Kosciuch, D. J. Tanner, F. L. Eisele, Chemical ionization mass spectrometer instrument for measurement of Tropospheric HO2 and RO2, Analy. Chem. 75, 5317-5327, doi:10.1021/ac034402b, 2003.
A23A-14
Measurement of Ammonia Species in Both Urban and Rural Environments
Ammonia plays an important role in atmospheric aerosol formations. The information of gas-phase ammonia (NH3) and particulate ammonium (NH4+) is essential in our understanding of atmospheric particle formation dynamics. Here we present ambient NH3 and NH4+ measurement results in two field campaigns, one at a rural site in Pinnacle State Park in Addison, NY, in the summer of 2004, and the other at a urban site in Downtown Albany, NY, in the summer of 2005. Air sample was collected by wet scrubbing, derivatized via Berthelot's reaction and quantified by a long path absorption photometer. At the rural site, NH3 mixing ratios were in the range of 0.1 - 5.3 ppbv with a median of 0.48 ppbv and a mean of 0.57 ppbv. The NH4+ concentrations in aerosol phase were in the range of 0.03 - 6.6 ppbv with a median of 0.81 ppbv and a mean of 1.3 ppbv. The aerosol NH4+ was the dominant NHx species most of the time. In Downtown Albany, NH3 mixing ratios were in the range of 0.1 -1 0.9 ppbv with a median of 1.6 ppbv and a mean of 1.6 ppbv. The NH4+ concentrations in aerosol phase were in the range of 0.03 - 9.38 ppbv with a median of 1.5 ppbv and a mean of 2.0 ppbv. The average NH3 and NH4+ mixing ratios were comparable, but their ratio was highly dependent on local source emissions and correlated with meteorological conditions. Factors controlling the NHx distribution will be discussed.
A23A-15
Ozone variations for Brisbane Australia and Mexico City over the period 1958-2004
Ozone variations over the period 1958 to 2004 for Brisbane, Australia and Mexico City, Mexico are presented in this paper. Ground-based total ozone data sets are compared with ERA40 and TOMS and used to estimate the total ozone variations. A significant spectral peak at wavelength between 10-11 years which corresponds to the solar cycle was found in the series. The data sets were deseasonalized and the anomalies relative to the period pre-ozone-hole (1970-1980) were calculated. The data sets show changes in the rate of the total ozone decline during the 80's while the ozone decline during the 90's is fairly constant. Ozone decline related to volcanic eruptions is seen during the 80's and 90's. Tropopause temperature and 50hPa temperature data sets for the same period were also deseasonalized and the anomalies relative to the period pre-ozone-hole (1970-1980) were calculated. For both cities, a decline of the 50hPa temperature is seen during the 80's. For the tropopause temperature, Brisbane shows a decline during the 80's, while Mexico City shows an increase, which could be related to the impact of volcanic eruptions
A23A-16
Observations of the Valley of Mexico Basin Ventilation Through the Tenango del Aire- Amecameca Geographical Gap
Past air quality modeling exercises have suggested the existence of basin drainage flows which may transport Mexico City Metropolitan Area's air pollution plume outside the Valley of Mexico Basin. The MCMA-2006 field campaign offered the opportunity to study the basin ventilation through a geographical gap in the southeast mountains of the basin. A mobile monitoring lab was placed at the Tenango del Aire town, a unique site located in this gap for measuring the pass of air masses from (and towards) the MCMA to (and from) the Cuautla Valley. O3, CO, NOx, NOy, CH2O global and UV radiation and MLH were measured continuously during MILAGRO from March 2 until April 6, together with other chemical species. Complementary backward and forward trajectories were constructed for the site using MCCM in prognostic mode during MILAGRO. An exploratory analysis of the air pollution roses measured at Tenango showed a sharp dominance of two flow patterns: one from the north well associated with relatively higher levels of primary pollutants and ozone levels; and another one from the south typically associated with lower levels primary pollutants but not so low of secondary ones as ozone. On the other hand, measured CO data at Tenango were compared with CO data measured at one local monitoring station in the town of Ocuituco in the State of Morelos. Ocuituco is located to the south of Tenango towards the Cuautla Valley. The preliminary results suggest that the back and forth pass of air masses through the Tenango del Aire - Amecameca area can be an important process in the regional transport of air pollution between two valleys and their metropolitan areas within the Central Mexico region.
A23A-17
Hourly Fluctuations in Labile Soil Phosphorus in Response to Climate Variability in a Wet Tropical Forest, La Selva, Costa Rica
Tropical rain forests are one of the most productive ecosystems in the world and play a significant role in the global carbon budget. Changes in phosphorus cycling dynamics as a result of on-going climate change have the potential to limit productivity in this ecosystem. Our objective was to determine hourly patterns in labile soil phosphorus throughout the day and explore possible mechanisms driving these patterns. We conducted an in situ experiment on soils from a wet tropical forest at La Selva Biological Station located in N.E. Costa Rica. A variety of climatic and biotic variables including temperature, precipitation, PAR, soil temperature, soil moisture and soil respiration were measured in order to determine their effect on labile phosphorus. Our results indicate that labile phosphorus does vary significantly throughout the day in response to a combination of climatic variables. An understanding of the mechanisms driving phosphorus availability at fine temporal scales can provide a valuable indicator of long term trends in phosphorus cycling dynamics.