Deshler
Geerts
Haimov
Hervig
Kelly
Montague
Marwitz
Parish
Rodi
Snider
Vali
Each summer a series of southerly wind surges disrupt the predominantly northerly flow regime off the West Coast of the United States. The passage of such wind reversals is typically accompanied by a drop in temperature, a rise in surface pressure and the development of low stratus and fog which can disrupt significantly local maritime activities. The forcing of such southerly wind events has been the topic of debate for over a decade. Several interpretations have been offered including Kelvin wave dynamics, gravity current progression and ageostrophic downgradient flow. It is clear that the topography is fundamental to the initiation and development of these so-called Coastally-Trapped Disturbances (CTDs). The scientific objective of the proposed research is to employ the fully-instrumented Wyoming King Air research aircraft as an observational platform to measure the forcing terms in the horizontal momentum equation responsible for the behavior of the CTDs.
A Study of the Interaction of the Antarctic Katabatic Winds with the Synoptic Environment From the FROST Dataset, PI: Parish
Recent research has shown that the Antarctic katabatic wind regime plays and important role in the mass, momentum and heat budgets of the high southern latitudes. The persistent low level katabatic outflow is a significant component of a thermally-direct mean meridional circulation over the high southern latitudes. It has been noted that the strong seasonal surface pressure changes over Antarctica during both austral springtime and autumn periods are forced primarily by the diabatic heating/cooling of the elevated ice slopes and attendant modification in the katabatic wind regime. It has also been shown that synoptic events can act to modulate the intensity of the katabatic wind off the continent and that the cold air drainage plays an important role in the energetics of cyclonic disturbances about the continent periphery.
A study of the interaction of the Antarctic katabatic wind regime with the ambient synoptic environment is underway. Stimulus for the research comes from ongoing Antarctic research as well as the recent completion of the First Regional Observing Study of the Troposphere (FROST), an international program with emphasis on the assembly of databases for high southern latitudes during three special observing periods. A primary objective of the FROST program is to improve the understanding of atmospheric dynamics over and around the Antarctic continent with hope of improving forecast skill. This proposed research will utilize the detailed complement of observational datasets and operational model output from the FROST archive during the austral springtime and winter observing periods to examine the interaction of the Antarctic katabatic windfield with the synoptic environment to the north of the continent.
Cloud
Chemistry Studies at Elk Mountain Observatory,
PI Snider [Updated 20000929]
Overview - The Elk Mountain research facility is unique because of its frequent exposure to clouds. Cloud exposure and high wind speeds result in strong vertical gradients of cloud droplets and ice crystals at the mountain/atmosphere interface. The site is therefore ideal for examining interactions between cloudy atmospheres and the alpine environment. Because of climatological similarities to regions located at higher latitude, but lower elevation, data collected at the Elk Mountain can also be used to better understand polar atmospheric processes and polar atmospheric/biospheric interactions.
Recent Research - University of Wyoming research conducted at the Elk Mountain during the 1990's has consisted of the following themes: 1) atmospheric sulfur dioxide oxidation to sulfate (Snider and Vali, 1994), 2) trace gas volatilization from ice (Snider and Murphy, 1995; Snider and Huang, 1998), 3) atmospheric cycling of low molecular weight alcohols Huffman, 1999), and 4) atmospheric nitrogen deposition to alpine tundra soils (Lokupitiya et al., 2000).
Site Description - The Elk Mountain facility is located at the northern end of the Medicine Bow Mountain range in southeastern Wyoming. The facility consists of an observatory, located at the head of Halleck Creek in a small semi-circular basin (10,850 ft msl), and the Schaefer Hut located atop the western peak of Elk Mountain (11,000 ft msl). A short grass prairie dotted with cattle and sheep ranches surrounds Elk Mountain. Aspens grow in the transition between the prairie and the upper slopes of the mountain, Lodge Pole pine forests extend from 8,000 to 9,000 ft, sub alpine fir and spruce up to 10,500 ft, and tundra dotted with patches of krummholz occur above 10,500 ft. Elk Mountain and the surrounding mountain summits are immersed in orographic clouds with a frequency of 30% during the winter months and 3% during summer.
Access - The facility is located on property owned by the Department of Atmospheric Science and the University of Wyoming. The Department operates three Tucker Snow Cats which are used for wintertime travel from the base of the mountain to the facility. The mountain access road crosses several privately owned land sections and the University pays an annual access fee to The Elk Mountain Ranch Company (Peter E. Thieriot, General Manager). During summer, approximately 3 hours is required to travel from Laramie to the facility.
Facilities - The facility is supplied with line power from Carbon County Power and Light. All of the appliances, including the heating system, are electric powered. There is a small wind tunnel, a cold room, modern kitchen and bathroom facilities, and room for six adults.
Data Communication and Acquisition - Data communication to and from the facility is via cellular phone and modem. The data acquisition system consists of a robust Pentium-based personal computer, National Instruments acquisition hardware and software, and a signal conditioning system designed and built in-house. Data can be both archived and analyzed at the observatory.
Sensors - Meteorological and cloud physics sensors include ambient temperature, dew point temperature, wind direction and speed (at both the Schaefer hut and the observatory), and cloud liquid water content. There is also a nephelometer and several atmospheric chemistry monitors (SO2, O3, reactive nitrogen, and hydroperoxides) at the observatory. The chemistry instrumentation has been customized for making low-level measurements.
References -
Huffman, W.A., An investigation of the uptake of low-molecular weight oxygenated hydrocarbons during vapor depositional ice growth, Ph.D. Dissertation, University of Wyoming, 1999.
Lokupitiya, E., N.L. Stanton, R.S. Seville, and J.R.Snider, Effects of increased nitrogen deposition on soil nematodes in alpine tundra soil, accepted to Pedobiologia, 2000.
Snider, J.R., and G. Vali, Sulfur dioxide oxidation in winter orographic clouds, J. Geophys. Res., 99, 18713-18733, 1994.
Snider, J.R., and T. Murphy, Airborne hydrogen peroxide measurements in supercooled clouds, J. Geophys. Res., 100, 23039-23050, 1995.
Snider, J.R., and J. Huang, Factors influencing the retention of hydrogen peroxide and molecular oxygen in rime ice, J. Geophys. Res., 103, 1405-1415, 1998.
Analysis
of the Condensational Growth Process in Marine Stratocumulus during the
second Aerosol Characterization Study (ACE-2) Snider [Updated
20000929]
See these sites for background -
http://www.fu-berlin.de/iss/photoalb/ace.html
and
http://www.ei.jrc.it/ace2/
P.I. - Jeff Snider
Duration - January 1999 - January 2002
Project Description
Stratocumulus clouds play an important role in controlling radiative heating within the earth/atmosphere system. Previous studies have shown that stratocumulus reflectivity increases with increasing concentrations of a subset of the atmospheric aerosol population known as the cloud condensation nuclei or CCN. There is also scientific evidence suggesting a link between rainfall produced by stratocumulus and CCN concentration. The latter effect may increase stratocumulus persistence or change their morphology. The net effect of longer-lived and more reflective stratocumulus is less solar energy input into the earth/atmosphere system. The predicted global cooling effect is comparable to the warming expected to result from increasing atmospheric carbon dioxide. Understanding of these interactions requires improvements in our ability to measure and to also forecast the fraction of the aerosol population that acts as CCN within stratocumulus.
The development of realistic descriptions of the CCN and their activation to cloud droplets is confounded by several factors. First, modeling of the activation process requires a time step which is short relative to that used in meso- and larger scale meteorological models. Second, the vertical velocity field within stratocumulus is highly variable and therefore realistic descriptions of the activation requires model resolution in both the space and time domains which is currently not possible. Also, there is a gap in our understanding of how to relate measurements of the aerosol to the CCN. An important consequence of the latter deficiency is that models that attempt to go from descriptions of the aerosol size distribution, predicted by an algorithm which describes aerosol source and sink processes, to the CCN activation spectrum may produce inaccurate estimates of the cloud droplet concentration. These issues must be addressed when developing mechanistic descriptions of global climate and the degree to which it is being perturbed by increasing levels of both gaseous and particulate air pollution.
We are investigating the previously discussed issues with support from NSF ATM-9816119. Specifically, we are examining if cloud droplet concentrations measured within adiabatic regions of stratocumulus can be predicted using a parcel model initialized with aircraft measurements of updraft and the CCN. In addition, we also testing parameterized descriptions of the concentration of cloud droplets produced by the activation process and also conducting laboratory intercomparison studies using a static diffusion CCN measurement system, an aerosol mobility system, and an optical particle counter.
Studies of Severe Winter Storms (SSWW), PI: Marwitz
The objectives of this research are to increase our understanding of the following aspects of major winter storms:
The research utilizes data from the Modernized NWS Network, the NWS/NCEP gridded data, and the Wyoming King Air to increase our understanding of these important aspects of severe winter storms. This research is an extension of the earlier Winter Icing and Storms Project conducted in the Front Range of Colorado and Wyoming. The SSWW research area is expanded to include winter storms throughout the Midwest and High Plains.Theses and Dissertations
Pobanz, B., M.S., 1991: Conditions associated with large drop regions.
Celik, F., M.S., 1993: An airborne case study of an evolving KH wave.
Heffernan, E., M.S., 1994: A single Doppler case study of the effects of melting
Prater, E., Ph.D., 1994: Aircraft measurements of ageostrophic winds.
Wei, Y., M.S., 1994: Numerical simulation of the effects of melting during a blizzard.
Ashenden, R., M.S., 1996: Airfoil performance degradation in supercooled cloud.
Celik, F., Ph.D., 1997: Cloud droplet spectra broadening by Ostwald ripening.
Ashenden, R., Ph.D., 1997: Turboprop aircraft performance response to various conditions.
Cissell, D., M.S., 1998: Aspect ratios of major snow swaths.
Coleman, S.H., M.S., 1999: A case study of freezing rain.
Wyoming King Air Aircraft as a National Facility, PI: Rodi
The Wyoming King Air is operated as a "flying laboratory" in which the onboard team (pilot, scientist, and data system operator) conducts interactive research into atmospheric processes. Since being placed in service in 1977, this Beechcraft Super King Air 200T (N2UW) and its predecessors have been used to conduct airborne research in over half of the 50 states, plus Canada, Spain, Mexico, Saudi Arabia, japan, and the Gulf of Mexico.
This twin-engine turboprop aircraft was purchased new and instrumented by the UW Department of Atmospheric Sciences to support cloud physics and weather modification research for the Bureau of Reclamation. Since 1988 it has been funded as a National Facility through a series of cooperative agreements between NSF and UW. As a national facility, the aircraft is available to all scientists on a competitive basis. NSF and ONR sponsored scientists are given priority.
A partial list of organizations and universities which have used this aircraft includes BuRec, ONR, NOAA, NCAR, NASA, FAA, plus about 15 major universities.
Airborne Air Quality Studies, Co-PIs: Montague/Snider
Increasing air pollution and associated visibility degradation are issues of growing concern throughout the western United States. Here in Wyoming public speculation on the impact of industrial development has increased in the last few years. We have recently addressed some of these issues by carrying out an airborne investigation of air quality in southwest Wyoming (March 1996) using the Wyoming King Air. In addition to making a complete suite of airborne meteorological observations, we also characterized the optical properties of the atmosphere, and the physical and chemical nature of particulates and other air pollutants. The observations complement those now being made at ground sites in the Green River basin. Data analysis is anticipated to continue for several years. The measurements should allow us to determine the contributions of both in-state and out-of-state sources to the observed pollutant loadings in the region. In addition, we plan to assess the potential for long range pollutant transport to pristine areas downwind of the study region. One further anticipated outcome of the study is the establishment of a baseline air quality information database that will provide a framework for assessments of environmental impacts resulting from future industrial development in the region.
Theses and Dissertations
Gunter, R.L., M.S., 1993: Characterization of the Optical Properties of California Aerosols During SJVAQS/AUSPEX.
Han, Z., M.S., (in progress):
Damiana, T., Ph.D., (in progress):
Carbon Sources and Sinks for Wyoming Ecosystems, Co-PI: Kelly
In a joint program involving the departments of Botany, Renewable Resources, and Atmospheric Science, fluxes of carbon dioxide, water vapor, and sensible heat were measured for a full seasonal cycle over four different ecosystems in southeastern Wyoming in 1999. The Wyoming King Air made eddy correlation flux measurements and collected air samples for carbon and oxygen stable isotope analysis. The primary focus of the project is to determine rates of carbon uptake and release for each ecosystem throughout the year. Remote sensing data and plant-cover archives are being used to scale up from the local measurements and assess the importance of these ecosystems in regional and global carbon budgets. In addition, measurements with a multi-channel spectrometer on the King Air have been combined with the flux data to show positive, linear correlations between the normalized difference vegetation index and surface CO2 flux for each site. A proposal to continue this collaboration has been submitted to NSF, to investigate processes and conditions that limit and govern plant- and landscape-scale carbon exchange, including the role of the atmosphere. [Updated 9/28/2000]
Studies of Clouds and Precipitation with Airborne Millimeter Wavelength Radar, Co-PIs: Vali/Kelly [Updated 20000929]
This is a long term effort to further develop and improve the airborne 95 GHz radar, the Wyoming Cloud Radar (WCR), and to use that radar for studies of clouds and precipitation. Part of this work is in collaboration with the Microwave Remote Sensing Laboratory (MIRSL) of the University of Massachusetts at Amherst.
In 1998, the radar was taken to France, mounted on a French research aircraft, and operated in projects TRAC98 and CLARE98 with two down-looking antennas in an innovative study of cumulus convection. Within project WYICE, flights with the King Air and radar focused on observations of lenticular, convective, and stratiform clouds. Hardware and software modifications in 1998 lead to improved sensitivity and an increase the number of polarimetric measurements available for analysis.
A proposal for further research with the King
Air/radar combinationhas been submitted to NSF, emphasizing the addition
and use of a second antenna for dual-beam, dual-Doppler measurements of
cumulus dynamics, an investigation of updraft-CCN relationships at cloud
base, and the evolution of precipitation in various cloud types.
Leon, D., M.S., 1996: VAD Analysis of Airborne
Radar Data.French, J., Ph.D., 1999: Observations of Small Cumuli
with an Airborne Radar and InstrumentedAircraft.Wolde, M., Ph.D., 1999:
Studies of Ice Clouds Using a 95 GHz Airborne Radar.Leon, D., Ph.D., in
progress: Airborne Dual-Doppler Radar Studies of Stratus Entrainment
and Dynamics.Coastal Stratus,
Co-PIs:
Kelly/Vali [Updated 20000929]
Theses and Dissertations:Gill,
S. (in progress): Relationships Between Droplet Spectra, Drizzle
Formation, and Air Motion in Coastal Stratus.
Investigations of sulfate aerosols and polar stratospheric clouds using combined observations from UARS, AVHRR, and in situ optical particle counters. P I: M. E. Hervig, CoI: T. Deshler, Location: Laramie, Wyoming, Agency: National Atmospheric and Space Administration [Updated 10/3/2000]
Stratospheric sulfate aerosol affect climate through radiative forcing, and chemical balance through heterogeneous reactions. In addition polar stratospheric clouds (PSCs) are a key element in polar ozone loss processes. The upper atmospheric Research Satellite (UARS), which measures aerosols and many key chemical species, was placed in orbit in 1991 three months after the eruption of Mt. Pinatubo increased stratospheric loading by a factor of 30. This proposal focuses on aerosol and gas measurements from two instruments on UARS, on measurements from another satellite instrument, the Advanced Very High Resolution Radiometer (AVHRR), and on measurements from balloon-borne optical particle counters to form a comprehensive look at stratospheric aerosols and PSCs. The work will include an extensive study of the global evolution of the Pinatubo aerosol cloud and a comprehensive study of PSCs.
Theses and dissertations:
Liu, Chuntu, MS, August 2000, Inferences of the composition of polar stratospheric clouds from the analysis of HALOE observations.
Hervig, M. E., and T. Deshler, Stratospheric aerosol surface area and volume inferred from HALOE, CLAES, and ILAS measurements, J. Geophys. Res., 103, 25345-25352, 1998.
Investigations
of sulfate aerosols and polar stratospheric clouds using combined observations
from UARS, AVHRR, and in-situ optical particle counters,
Co-PI’s: Hervig/Deshler
Stratospheric sulfate aerosol affect climate through radiative forcing and chemical balance through heterogeneous reactions. In addition, polar stratospheric clouds (PSC’s) are a key element in polar ozone loss processes. The Upper Atmospheric Research Satellite (UARS), which measure aerosols and many key chemical species, was placed in orbit in 1991, three months after the eruption of Mt. Pinatubo increased stratospheric loading by a factor of 30. This proposal focuses on aerosol and gas measurements from two instruments on UARS, on measurements from another satellite instrument, the Advanced Very High Resolution Radiometer (AVHRR), and on measurements from balloon-borne optical particle counters to form a comprehensive look at stratospheric aerosols and PSCs. The work will include an extensive study of the global evolution of the Pinatubo aerosol cloud and a comprehensive study of PSCs.
Theses and Dissertations
Hervig, M.E., Ph.D., 1997: The physical properties of stratospheric aerosols determined from HALOE observations.
Cirrus Detection by Solar Occulation, PI: Vali
The solar occultation data produced by the SAGE II satellite offer the possibility of detecting cirrus of low optical thickness. Development of methods for detecting and characterizing the cirrus or other upper tropospheric clouds is the principal goal. The methods will also be applied to data derived from the SAGE III satellite to be launched in 1999.
Theses and Dissertations
Jia, J., M.S., 1991: Cirrus cloud observations from tangent path measurements of solar extinction.
Fan, D., M.S., 1993: Tropospheric aerosol profiles from SAGE II solar extinction observations.
Gill, J., M.S., (in progress)
HALOE Algorithm Improvements for Upper Tropospheric Sounding. PI(UW) Mark Hervig; P I: Larry Gordley, GATS Inc.
This work will improve and augment the HALOE processing algorithms to retrieve high quality H2O, CH4, and ozone down to the middle troposphere and NO and HCl into the upper troposphere.
The HALOE instrument on UARS has been making measurements since October 11, 1991. Both hardware and data processing algorithm were designed to optimize success in achieving the original goals of measuring HF, HCl, CH4, NO, NO2, H2O, and O3 in the stratosphere and mesosphere. It has equaled or exceeded these goals in both altitude range and quality. In addition, aerosol extinction in four bandpasses plus independent temperature above 30 km were sucessfully added to the product list.
The algorithm development and signal analysis
team has recently overcome obstacles to extending the O3, CH4, and H2O
data sets into the troposphere. These obstacles include understanding of
instrument tracking performance, cloud signal analysis, and forward model
limitations. With solutions to these obstacles now in hand, the development
team can proceed to develop and implement a robust tropospheric analysis
with very little risk. Key members of the HALOE science and algorithm development
teams will perform the work using HALOE project facilities and culminating
in the delivery of a final HALOE data processing system to the UARS CDHF
in the late summer 2000. This work will improve the accuarcy of the lower
stratosphere data and add new data on important climate parameters in the
troposphere.
Development of Microwave Atmospheric Remote Sensing Facility (MARSF) PI: Haimov, Co-PIs: Kubicheck, Vali
This project is a joint effort by the Departments
of Atmospheric Science and Electrical Engineering. Our objective
is to develop a mobile laboratory for training and education of students
and research staff in advanced microwave remote sensing instrumention.
MARSF will be housed in a mobile trailer and will include the (http://www.atmos.uwyo.edu/wcr/)
Wyoming
Cloud Radar (WCR) and a dual-frequency microwave radiometer (MR).
Another important purpose of this facility will be to provide test and
devolpment opportunities for the WCR/MR under regular operating conditions
in ground installation.
Interaction between cloud streets and gravity waves during cold air outbreaks over water [‘proposal in preparation’] . PI: Geerts; co-PI: Foster, Brown, Schwemmer, Flamant
Streets of boundary-layer stratocumulus are commonly observed when a continental cold air mass is advected over relatively warm water. It is not surprising, therefore, that undulations exist on the PBL inversion capping these clouds. What is surprising is that these undulations appear to extend deeper into the troposphere. This observation may explain why cloud streets have been observed with aspect ratios that cannot be explained by any of the competing dynamical theories for cloud streets. Do gravity waves aloft modulate the spacing and orientation of cloud streets? Do cloud streets in turn exert gravity wave drag onto the deep troposphere ? Does the secondary cloud-street circulation add significantly to the vertical energy transfer across the PBL? To answer these questions, an experiment (COWEX-II) has been proposed to simultaneously detail cloud streets and gravity waves aloft. We hope to conduct this experiment in Nov-Dec 2003 from Wallops, VA, and will deploy a NASA P-3 and the UW King Air and Wyoming Cloud Radar, amongst others.
URLs:
COWEX-II - http://www.atmos.uwyo.edu/~geerts/cowex/
WCR - http://www.atmos.uwyo.edu/wcr/
Validation of a spaceborne 95 GHz cloud radar. Investigators: Geerts, Vali, Kelly, Snider, Rodi, Leon.
The 95 GHz cloud profiling radar is the centerpiece of the CloudSat satellite, to be launched in April 2004. CloudSat will fly in orbital formation as part of a constellation of satellites including Aqua and Aura (multi-sensor platforms that are a part of NASA's Earth Observing System), ESSP3 (which will carry a cloud-observing lidar), and PARASOL (carrying a polarimeter). Funding has been received from NASA to study characteristic fine-scale cloud patterns using the Wyoming Cloud Radar (WCR), an airborne 95 Hhz radar. A nadir port is being added to the UW King Air to allow nadir WCR measurements, i.e. from the same vantage point as CloudSat. Two field campaigns are planned in the next few years to obtain WCR reflectivity and vertical velocity profiles, combined with in situ cloud and flux measurements.
URL’s:
CloudSat- http://cloudsat.atmos.colostate.edu/
Dynamics of radar fine-lines in the pre-convective continental boundary layer [pending]. Investigators: Geerts, Leon, Koch
The Wyoming Cloud Radar, aboard the UW King Air, will participate in the International Water Vapor Experiment (13 May- 30 June 2002 in Oklahoma-Kansas) which aims to bring together the latest technologies to document the detailed 4-D water vapor structure and its impact on convective initation. Thunderstorms are often triggered along shallow convergence lines. These "fine-lines" can be seen by operational radars, generally because of the high resident insect concentrations. The WCR will primarily operate in a vertical-plane dual Doppler mode, allowing the derivation of the flow field in the two dimensions of a vertical cross-section below the aircraft. King Air observations are part of a broad effort involving several aircraft, mobile and fixed ground facilities. We plan to use data from the King Air, the WCR, and other platforms to document the structure and evolution of radar fine-lines, and to dynamically interpret the observations through state-of-the-art 4DDA and modelling work in collaboration with NOAA Forecast Systems Lab.
URL’s:
IHOP - http://www.atd.ucar.edu/dir_off/projects/2002/IHOP.html
WCR - http://www.atmos.uwyo.edu/wcr/
FSL-LAPS - http://laps.fsl.noaa.gov/