HR: 14:30h
AN: A33B-03    [Abstracts]
TI: Convective Heating and Moistening Within the Interior of the NAME Domain
AU: * Johnson, R H
EM: johnson@atmos.colostate.edu
AF: Department of Atmospheric Science, Colorado State University, Fort Collins, CO 80523, United States
AU: Ciesielski, P E
EM: paulc@atmos.colostate.edu
AF: Department of Atmospheric Science, Colorado State University, Fort Collins, CO 80523, United States
AB: Atmospheric sounding, aircraft, pibal, and surface observations taken during the 2004 North American Monsoon Experiment (NAME) have presented the opportunity to investigate the nature of convection and its diurnal cycle in the monsoon region of northwest Mexico, a region that has heretofore been poorly sampled. The core of the NAME domain, which is the focus of this study, is characterized by steep orography in proximity to a coastline in a moist, tropical environment. Much of the world's heaviest rainfall occurs in such environments, so the results of this study have broader implications than just those applicable to the NAME region. The sounding and surface observations have been quality-controlled and assembled to produce a gridded data set over the NAME domain. In order to obtain a proper lower boundary condition to compute vertical motion over the slopes of the central mountain range of Mexico (the Sierra Madre Occidental or SMO), surface and pibal data, albeit sparse, were used to describe the boundary-layer and low-level flow. Divergence and vertical motion were then computed within sounding polygon areas encompassing both land and ocean (Gulf of California) regions. The land polygon overlapped the domain of the NCAR S-Pol radar deployed north of Mazatlan. Results show a prominent sea breeze, land breeze cycle along the west slopes of the SMO. There is a deep return flow above the afternoon sea breeze as a consequence of the elevated SMO immediately to the east. Subsidence produces a dry layer in the afternoon over the Gulf of California, while a deep moist layer exists over the western slopes of the SMO. The diurnal cycle of apparent heating and moistening (Q1 and Q2) over the SMO is characterized by deep-convective profiles in the mid-to-upper troposphere at 1800 LT, followed by stratiform- like profiles at midnight, consistent with the observed diurnal evolution of precipitation over this coastal mountainous region. Unlike experiments such as GATE and TOGA COARE, cooling is observed in the lower troposphere in the mean profiles of Q1, likely due to more evaporative cooling from drier conditions at low levels over land compared to those over tropical oceans. The diagnosed fields and budgets from the gridded analyses, which are completely independent of model data, will be compared to those from a special North American Regional Reanalysis (NARR) prepared specifically for NAME. Explanations for the differences will be explored.
DE: 3310 Clouds and cloud feedbacks
DE: 3314 Convective processes
DE: 3329 Mesoscale meteorology
DE: 3355 Regional modeling
DE: 3374 Tropical meteorology
SC: Atmospheric Sciences [A]
MN: 2007 Joint Assembly