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In the Earth system, the land surface and atmosphere interact in two important ways: exchange of energy and exchange of mass. Solar energy absorption at the surface dominates the surface energy exchange. How this solar energy is partitioned into other forms of energy (infrared radiation, ground heat conduction, atmospheric sensible heat, and atmospheric latent heat) has significant implications for weather and climate. For example, deserts and rainforests have distinctly different climates although they may receive the same amount of solar energy. Solar radiation also influences mass exchange, in particular, the exchange of water through evaporation and condensation. The presence of water directly impacts climate, and in fact, helps define different climate regimes (dry or wet).
My research largely involves understanding the role of surface processes (exchange of energy and water) on the development of clouds, thunderstorms, and extreme precipitation. These studies include both observations and computer simulations. Surface energy balance observations are taken at the Austin College Weather Station, a meteorological research station established by undergraduate students. Computer simulations have been conducted using sophisticated atmosphere-land surface models developed at NASA Goddard Space Flight Center.
Austin
College Weather Station : Surface energy balance
measurements provide unique opportunities for undergraduate
students to become
involved in Atmospheric and Environmental Physics research.
NASA's KWAJEX Field Campaign : This project in the Marshall Islands collected atmospheric data to help calibrate NASA's Tropical Rainfall Measuring Mission (TRMM) satellite.
1993 US Midwest Flood: Computer simulations suggest that the land surface was not a primary factor in producing the heavy rainfall associated with the historic 1993 Midwest floods.
6-7 May 2000 Missouri Flash Flood: Computer simulations suggest that soil moisture influences the development of a low-level jet (LLJ) from the Gulf of Mexico that injects moisture into a storm that produced 34 cm (13 inches) of rain in 8 hours.
Soil Moisture, Coastline Curvature, Land Breezes, and Florida Thunderstorm Development : Computer simulations suggest that pre-existing soil moisture has a significant impact on the timing and location of precipitation in Florida.The curvature of coastlines helps focus precipitation in certain areas, and pre-existing land breezes in the early morning alter the timing of precipitation.
Sea-Breezes and Convection in Florida: A new computer model shows that realistic soil moisture distribution is required to reproduce precipitation patterns in Florida.
Sea-Breeze Initiated Thunderstorms in Darwin, Australia:
Computer simulations suggest that a negative feedback exists in
which heavy precipitation can inhibit the development of precipitation
on the
next day.
Land Use and Convective Precipitation in the African Sahel Region: Computer simualtions indicate that a positive feedback exists in the African Sahel: less rainfall produces drier conditions which makes the region more desert-like which, in turn, produces less rainfall, which produces even drier conditions...
Cloud Resolving Modeling: Signfiicant advances in modeling capabilities have occurred over the past decade. This paper highlights improvements in a sophisticated cloud-land surface model developed at NASA Goddard.
Stability of the Long-term Carbon Cycle: This project involves nonlinear modeling of the carbon cycle to detect possible chaotic behavior in the Earth system.
Planetary science is a diverse interdisciplinary science involving physics, chemistry, geology, meteorology, astronomy, and biology. My research interests involve the dynamics of planetary atmospheres: how and why they move the way they do. My research utilizes state-of-the-art computer models and recent spacecraft observations to understand the atmospheres of different planets, in particular, the atmospheres of Venus, Jupiter, and Mars.
Venus
Convectively Generated Gravity Waves in Venus's Atmosphere: No Mean Wind : Computer simulations suggest that wave patterns in the atmosphere of Venus are produced by strong convection in the clouds roughly 50 km above the surface.
Convectively Generated Gravity Waves in Venus's Atmosphere: Mean Wind Shear and Wave-Mean Flow Interaction : Waves produced by convection in the cloud layer at 50 km altitude and convection deeper in the atmosphere at 30 km altitude alter the mean winds between the two convection layers.
Penetrative Convection in Venus' Atmosphere : Computer simulations show that convection in the cloud layer of Venus can penetrate deeply into the lower atmosphere. Surprisingly, downdrafts of cold air are stronger than warm updrafts.
Turbulent (High Rayleigh Number) Convection in Venus' Atmosphere: More realistic computer simulations suggest that convection at the subsolar point (noontime at the equator) may erode stable layers above and below the cloud layer.
Venus convection: Warm colors indicate warm air, cool colors indicate cool air.
Jupiter
- Downdrafts in Jupiter's Atmosphere: Strong convective downdrafts may help explain dry "hot spots" that comprise about 1% of Jupiter's atmosphere (the Galileo probe entered one of these hot spots).
Mars
- Dust Devils in the North Polar Region of Mars: Observations of dust devil tracks and wind streaks from the Mars Global Surveyor spacecraft show a plethora of activity in the North polar region of Mars, the location of the 2007 Mars Phoenix Lander landing site.
A) Linear dust devil tracks, B) curvy dust devil tracks, C) wind streaks, and D) cloud shadows.
I want students to think like scientists. I want to inspire students to learn and explore in their own way, to attempt to answer their own questions, and not to be afraid of failure as they find their own answers. Most importantly, I want learning to be fun. To this end, I have become involved in Education Research, bot h in Physics and in Earth System Science.
Scientific Inquiry Portfolios: Students make their own scientific observations, ask their own questions, develop their own hypotheses, and conduct their own scientific experiments. Throughout the process, the portfolio measures an individual student's scientific growth. Portfolios have been used effectively in introductory non-science major courses through senior-level physics courses.
Project-Based Learning, Surface Energy Balance, and a New Weather Station: I use project-based learning in many of my courses. In this example, students conducted a semester-long research project to establish the Austin CollegeWeather Station. The next semester, students conducted an 8-week project to calibrate and validate the measurements. In both cases, students likely had a more positive learning experience than if they had taken a traditional meteorology or physics course.
Design Guide for Undergraduate Earth System Science Education: With faculty members from across the country, I helped develop a design guide for faculty and administrators interested in developing Earth System Science courses and programs. I authored the Teaching, Learning, and Evaluation section of the Design Guide. Innovative learning approaches from over 130 Earth System Science courses are highlighted. Please check it out!
