Research

SHEBA May 4 aircraft flight shown projected upon a cloud radar reflectivity time-height diagram, relative to the lidar-determined water cloud base (dotted line) and temperature inversion (solid line). see Zuidema et al. (2005) for further explanation.	The Arctic: An important result from the Surface Heat Budget of the Arctic experiment is that clouds are often mixed-phase. While the liquid component is primarily responsible for the cloud optical depth and thereby the radiative cloud forcing at the surface, ice initiation acts to regulate the presence of liquid. I am working to provide observational constraints on ice-initiation processes using SHEBA data. Inspired by the radiative importance of the liquid phase, Robert Joyce and I are also evaluating satellite microwave-derived liquid water path climatologies and trends over the northern high latitude open seas. Both these projects are funded under a NASA Interdisciplinary Studies grant.
Zuidema et al. (2006) is a writeup of the EPIC analysis	The Tropics: Tropical clouds attain complex structures, reflective of the many processes that help form them. I am elucidating tropical cloud vertical structure from two tropical oceaninc field campaigns. Within the eastern tropical Pacific, mid-tropospheric dry air of equatorial origin can impinge upon and feedback with overlying cirrus anvils. In contrast, within the Bay of Bengal the atmospheric moisture distribution switches completely from dry to moist at monsoon onset, with two highly different associated cloud vertical structures. The different behaviors are evident in cloud radar reflectivities shown overlain with rawindsonde relative humidities and winds and contours of the divergence calculated from coincident precipitation radar, along with measured surface rainfall rates. Eastern Pacific Investigation of Climate (EPIC) (11 Mb pdf) Joint Air-Sea Monsoon Experiment (JASMINE; Bay of Bengal) (12 Mb pdf). Note to other researchers: The EPIC data are publicly available through http://catalog.eol.ucar/edu/epic. The JASMINE data are also publicly available but harder to find. Try http://www.esrl.noaa.gov/psd and http://www.atmos.washington.edu/MG/JASMINE/jasmine.html.
Zuidema et al. (2005) contains an assessment of surface-based liquid water paths gathered during the EPIC stratocumulus leg.	The Subtropics: The relationship between subtropical boundary-layer cloud properties, precipitation, and aerosol is still not well-understood. Under a NOAA grant, David Painemal and I are working with data from buoy-tending cruises to the southeastern Pacific stratus region to elucidate these associations and assess satellite-retrieved information with ship-based data. These almost-annual cruises are conducted by Chris Fairall (see http://www.esrl.noaa.gov/psd/psd3/). In another NASA-funded project I am assessing the three-dimensional radiative transfer behavior of trade-wind Cumulus under varying aerosol regimes. The cloud data come from LES simulations undertaken by primarily by Huiwen Xue and Graham Feingold.
Mean diurnal cycle in sonde relative humidity and ceilometer cloud base heights over the southern Gulf of California during NAME, described more fully in Zuidema et al. (2007).	Field investigations in the Southeastern Pacific stratocumulus region and the North American Monsoon highlight the importance of light evaporating precipitation to the dynamics of each region. A confident knowledge of the precipitation and its flux remain lacking for both regions. A newly-funded NOAA (2007) project will address this through developing a precipitation retrieval for both locations from vertically-pointing lidar (ceilometer) data. I am looking to employ a graduate student on this project, and invite interested people to contact me and apply to U of Miami/RSMAS/MPO.