Professor Sonia Lasher-Trapp
Purdue University Department of Earth & Atmospheric Sciences
Research Areas
Observations
The Cloud Microphysics Group also conducts research on clouds and precipitation processes by collecting and analyzing observations. Observations of clouds and precipitation are acquired remotely, using highly sensitive weather radars or satellites, and directly, by mounting instruments on aircraft and then flying through the clouds at different spatial locations and stages of cloud development. We usually participate in large-scale, multi-university and/or multi-agency field campaigns that collect cloud observations over a variety of scales. As in the modeling, part of the challenge is to synthesize the information collected at different scales into a coherent picture of cloud and precipitation evolution.
A vertical cross section of a cumulus cloud taken by a research weather radar is shown at the figure below. Highly-sensitive research weather radars are able to detect the smaller cloud droplets and the development of larger drops (precipitation) by the intensity of the radar signal. The pink in this figure indicates the outline of the cloud; the different levels of green indicate where (and when) precipitation is beginning to develop (and fall) within this cloud.
Data on the cloud structure, its dynamic and thermodynamic properties, as well as the kinds of cloud and precipitation particles it contains, can all be collected. Time series data (shown below) as well as shadows or images of particles are collected. These limited data must then be assembled into an overall picture of the cloud characteristics and their evolution-- not an easy task, but a necessary one to understand what "really" occurs in natural clouds.
An example of time series data collected as an aircraft flies through a cumulus cloud. From top to bottom: total number of drops, amount of liquid water, updraft speed, and aircraft speed while sampling. Note the homogeneity within the cloud and the large variance of the cloud properties at the cloud edges.
