Fitting microphysical observations to a numerical model through an optimal control theory technique

March 26, 1992.Also issued as author's dissertation (Ph.D.) -- Colorado State University, 1992.Includes bibliographical references.Rapid advances in the quality and quantity of atmospheric observations have placed a demand for the development of techniques to assimilate these data sources into numerical forecasting models. Four-dimensional variational assimilation is a promising technique that has been applied to atmospheric and oceanic dynamical models, and also to the retrieval of three-dimensional wind fields from single Doppler radar observations. This study investigates the feasibility of using four-dimensional variational assimilation for a complex discontinuous numerical model. Three test models were developed, a positive definite advection scheme, a one-dimensional liquid physics kinematic microphysical model with a positive definite advection scheme, and a two-dimensional liquid physics kinematic microphysical model. These models were used in identical twin experiments, with observations taken intermittently. Small random errors were introduced into the observations. The retrieval runs were initialized with a large perturbation of the observation run initial conditions. All the models were able to retrieve the original initial conditions to a satisfactory degree when observations of all the model prognostic variables were used. Greater overdetermination of the degrees of freedom (the initial condition being retrieved) resulted in greater improvement of the errors in the observations of the initial conditions, but at a rapid increase in computational cost. Experiments where only some of the prognostic variables were observe also improved the initial conditions, but at a greater cost. To substantially improve tie first guess of the field not observed, some spot observations are needed. The proper scaling of the variables was found to be important for the rate of convergence. This study suggest that scaling factors related to the error variance of the observations give good convergence rates. To show how this technique can be used when observations are general functions of the prognostic variables of the model (e.g. reflectivity or liquid water path), a form is derived which shows that this can be accomplished. This is considered to be an advantage of this technique over others, since it is particularly suitable to remote sensing systems where only integral parameters or derivatives of model prognostic variables are observed.Sponsored by the South African Weather Bureau, Dept of Environment Affairs; the National Science Foundation ATM-8814913; and the Army Research Office DAAL03-86-K-017

Final Technical Report

The research project focuses on the following topics: a) removal of artifacts in the Doppler spectra from the ARM cloud radars, b) development of the second generation Active Remote Sensing of Cloud Layers (ARSCL) cloud data products, and c) evaluation of ARM cloud property retrievals within the framework of the EarthCARE simulator. We continue to pursue research on areas related to radiative transfer, atmospheric heating rates and related dynamics (topics of interest to the ARM science community at this time) and to contribute on an ad-hoc basis to the science of other ARM-supported principal investigators

CSU-RAMS cloud microphysics module: general theory and code documentation, The

September 1, 1989.Includes bibliographical references

Tropical Convection's Roles in Tropical Tropopause Cirrus

The results presented here show that tropical convection plays a role in each of the three primary processes involved in the in situ formation of tropopause cirrus. First, tropical convection transports moisture from the surface into the upper troposphere. Second, tropical convection excites Rossby waves that transport zonal momentum toward the ITCZ, thereby generating rising motion near the equator. This rising motion helps transport moisture from where it is detrained from convection to the cold-point tropopause. Finally, tropical convection excites vertically propagating tropical waves (e.g. Kelvin waves) that provide one source of large-scale cooling near the cold-point tropopause, leading to tropopause cirrus formation

Decisão em Condições de Incerteza Meteorológica e Proteção de Infraestruturas no Centro de Lançamento de Alcântara

Resumo A tomada de decisão utilizando informações meteorológicas muitas vezes é um processo complexo, de alto impacto e, em algumas situações, pode comprometer o funcionamento de instalações tecnológicas. Neste contexto, o objetivo deste artigo é apresentar uma abordagem de apoio à decisão em condições de incerteza meteorológica para a proteção das infraestruturas no Centro de Lançamento de Alcântara. A partir de uma demanda operacional, foi desenvolvido um índice meteorológico de modo a identificar a atitude dos decisores em relação às três características da informação meteorológica: a) probabilidade da previsão de tempo; b) prazo de validade; c) valor da variável atmosférica. Como estudo de caso, foi analisado um problema real de decisão para proteção das instalações do principal centro espacial brasileiro. Através da interação com os usuários na construção do índice, foi possível concluir que para probabilidades baixas ( 24 h), o grupo de usuários entrevistados não utiliza a informação meteorológica para tomar decisões, mesmo com o prognóstico de condições extremas. Os resultados quantitativos demonstraram que o modelo de apoio à decisão proposto conseguiu incorporar a atitude do usuário não-meteorologista em relação à incerteza da informação meteorológica

Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) Field Campaign Report

USDOE Office of Science (SC), Biological and Environmental Research (BER)U.S. Department of Energy, DOE/SC-ARM-18-00

January 2016 extensive summer melt in West Antarctica favoured by strong El Niño.

Over the past two decades the primary driver of mass loss from the West Antarctic Ice Sheet (WAIS) has been warm ocean water underneath coastal ice shelves, not a warmer atmosphere. Yet, surface melt occurs sporadically over low-lying areas of the WAIS and is not fully understood. Here we report on an episode of extensive and prolonged surface melting observed in the Ross Sea sector of the WAIS in January 2016. A comprehensive cloud and radiation experiment at the WAIS ice divide, downwind of the melt region, provided detailed insight into the physical processes at play during the event. The unusual extent and duration of the melting are linked to strong and sustained advection of warm marine air toward the area, likely favoured by the concurrent strong El Niño event. The increase in the number of extreme El Niño events projected for the twenty-first century could expose the WAIS to more frequent major melt events