Observing and Understanding the Variability of Water in Weather and Climate


Inferring convectively-induced roll structures and convergence in the boundary layer using profiling instruments: An application to convective initiation during IHOP_2002

John R. Mecikalski, CIMSS/Univ. of Wisconsin, Madison, WI; and K. M. Bedka, R. D. Torn, W. F. Feltz, and T. M. Weckwerth

The goal of this study is to present new methods for inferring the patterns of three dimensional turbulent and water vapor structures within the convective boundary layer (CBL; e.g. convectively driven rolls, significant wind convergent-induced boundaries) from one-dimensional profiles of temperature, moisture and wind. Such structures, as formed in deepening CBLs under the influence of solar heating, provide the first clues to how deeper, precipitating convection may form. Obtaining three-dimensional information from profiling instruments has benefits when more elaborate radar measurements are not available.

Two approaches are taken toward evaluating how one-dimensional profiles measure three-dimensional convective features: 1) Use time series analysis to relate the statistics of one-dimensional profile measurements to the anticipated statistics of three-dimensional structures. Specifically, we quantify the subtle variations in heat and moisture associated with rolls as they move over a stationary profiling instrument to assess the period, size and orientation of CBL rolls. This statistical analysis is then compared to rolls as they appear in radar or satellite data. Subsequent analysis of quantities such as the Richardson number (based on the stability and shear within a CBL) allow us to evaluate how CBL turbulence should organize and evolve in a given set of meteorological conditions. 2) Directly compare how observed turbulent structures (measured by profiling instrument) statistically compares with modeled structures using large-eddy simulation (LES) experiments, and observed roll and boundary features as measured by high-resolution satellite imagery and radar data. This analysis again helps infer what CBL properties profiling instruments are measuring.

An additional question that this study will address is the time scales and mechanisms of surface-based moisture- and wind-convergent boundary formation and decay within the CBL wind fields as related to roll evolution, cloud line formation and convective initiation. This will occur as observational analysis are combined with LES experiments for selected days during IHOP_2002.

The IHOP_2002 data sets to be employed for this work include 1 km resolution GOES-11 imagery, S-Pol radar reflectivities, AERI and lidar profiler data, and data generated by the University of Wisconsin Nonhydrostatic Modeling System (UW-NMS) performing LES experiments. The poster will present our progress to date.

extended abstract  Extended Abstract (444K)

Poster Session 1, International H20 Project (IHOP)
Monday, 10 February 2003, 2:30 PM-2:30 PM

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