1995: Clouds and Storm Lifecycles

Research by students from A. Philip Randolph High School, Brooklyn Polytechnic, and City College of New York
GISS scientist: Anthony Del Genio

Summary of Previous Work

This team focused on clouds associated with midlatitude winter storms, and tropical hurricanes, two important types of cloud making weather systems. The project is concerned with understanding how clouds on Earth will respond to global climate warming in order to predict the timing and magnitude of climate change.

To study this problem the team investigated how cloud systems behave in the real world, and how well they are simulated in the GISS climate model. How clouds evolve over time, and whether the different types of storms have similar or very different types of clouds are key areas of interest for this research project. The team used actual weather data to identify candidate storms, and tracked the brightness and altitude of the cloud tops in concurrent satellite images of the storm area, both for several midlatitude winter storms, and for Hurricane Diana. Several data sets were used for this study, including: The International Satellite Cloud Climatology Project (ISCCP), global observations of clouds from an international constellation of weather satellites and the National Meteorological Center, global compilation and analysis of weather observations.

They identified typical storms in the GISS climate model as well, and tracked their variation with time to see how well the model simulates real world clouds. Storms in the model were identified manually by looking for low pressure centers, but the team compared these findings to those extracted from a computer program that automatically identified storms without human intervention. They are also developing pattern recognition techniques to determine whether the computer can be "taught" to identify real storms in satellite images using predictable aspects of the spatial patterns, and evolution in time of the clouds properties they produce.

Summer 1995 Objectives

Determine the typical structure of the cloud field in the midlatitude and tropical storms.

Method: Isolate storm areas in the model and the data midlatitudes and derive the mean properties (cloud cover, optical thickness and top temperature/pressure) of the clouds in these areas over the period of one month. Repeat the analysis over several years to derive a climatological structure for the months under consideration. Derive the mean properties of the clouds in tropical storms over a period of ten years.

Determine the differences in cloud-structures between storms in flood and drought seasons.

Method: Assign drought/flood teams consisting of a teacher and a student to examine the differences between the drought/flood storm-cloud properties and the storm-cloud properties in the climatological mean (or in an average year).

Determine the deficiencies in the way the GCM produces clouds in storms.

Method: Compare the typical sea-level pressure structures in model and data storm areas. Compare the mean cloud properties in model and data storms. Compare the drought/flood cloud anomalies of the model and the data.

Determine the contribution of model deficiencies in storm-cloud production to the radiative imbalance in the model midlatitudes.

Method: Estimate the contribution of storm-clouds to the radiative properties of the total cloud field in the model midlatitudes. Estimate the difference in the radiative balance that would be produced by a correction in the model storm-cloud field to fit the cloud data.