Atmospheric Chemistry Division

Advanced Study Program

ASP and the Mesoscale and Microscale Meteorology Division (MMM) hosted a summer colloquium in June 1999 on "Ice formation in the Atmosphere."  Charles Knight (MMM) coordinated the sessions which were held at NCAR. ASP concurrently used Web delivery to record and display the lectures of 20 people from 13 institutions of the U.S. and Canada.   The 21 student participants represented 14 institutions from 4 foreign countries and the U.S.  The colloquium addressed the microphysical processes involved in ice formation, the current status of observations of ice in various types of clouds, and the links between ice formation and chemical, electrical, and radiative properties of clouds as well as the current status of laboratory and theoretical evidence pertaining to ice formation and ice effects in models at various scales. (See http://www.asp.ucar.edu/colloquium/1999)

Atmospheric Technology Division

TOGA COARE Soundings Corrections

In the winter of 1992/93, nearly 12,000 radiosonde soundings were launched from 36 Priority Sounding Stations during the TOGA COARE Intensive Observing Period. Sounding systems provided by NCAR/ATD, including the Integrated Sounding Systems (ISS) of the central Intensive Flux Array (IFA), launched more than one third of those radiosondes. The combined sounding data set represents an unprecedented look at the atmosphere over and near the Western Pacific oceanic warm pool, allowing investigators to explore such issues as diurnal boundary layer variations, convective processes, dry intrusions, atmospheric heat and moisture budgets, synoptic-scale low-level westerly and upper-level easterly bursts and 30-40 day waves. Analysis, reanalysis, and modeling efforts worldwide have used and continue to rely on the TOGA COARE sounding data set.

During initial processing of the TOGA COARE sounding data, analysts suggested that radiosonde temperature and humidity measurements seemed too warm and too dry respectively in the lowest levels, at least during daytime soundings. ATD engineers attributed this warm dry bias to radiational heating of the temperature and humidity sensors and sensor arm just prior to balloon launch. NCAR then developed an algorithm and methodology to correct near-surface temperature and humidity data for this so-called sensor-arm heating and the corrections were applied to the COARE data set.

Further analyses of the TOGA COARE data indicated a residual dry bias not resolved by application of the sensor-arm heating correction. Some of these analyses showed large horizontal gradients of humidity and of derived parameters such as Convective Available Potential Energy (CAPE) despite the relatively uniform sea surface temperatures in the COARE IFA.

Scientists and engineers from ATD and from Vaisala (Helsinki, Finland), the manufacturer of most sondes used during TOGA COARE, confirmed the dry bias and identified its cause: contamination of the capacitance humidity sensor by various gaseous plastic and Styroform components. Based on extensive Vaisala testing, ATD and Vaisala developed a prototype correction algorithm based on physical characteristics of the humidity sensors. With additional funding from NSF and NOAA, the correction algorithm was further developed and has now been applied to almost all IFA soundings from TOGA COARE.

Vaisala has taken corrective actions since the problem has been discovered. A new desiccant, made of a mixture of silica gel and activated carbon, has replaced the clay-based drying agent. A protective sensor arm cover as added to the new sondes as well, which isolates the sensor from contaminants eliminating the bias.

The work on the TOGA COARE data set has been carried out by H. Cole, E. Miller, J.-H. Wang, D. Parsons, F. Guichard and K. Beierle, all ATD/SSSF.

Climate and Global Dynamics Division

For the first time climate change experiments have been carried out with a fully coupled climate model that employs no flux adjustments and shows no surface climate drift. These simulations also included interactive chemical effects that have previously been ignored or prescribed.

CSM simulations (30 K) of the 20th and 21st centuries have been carried out. For the 20th century, a control simulation, a transient simulation, a solar variability simulation including the reconstructed solar variation, and a greenhouse-gases only simulation were completed.  The project involved many participants and was led by J. T. Kiehl (NCAR), S. Solomon (NOAA Aeronomy Lab) , T. M. L. Wigley (NCAR), and B. A. Boville (NCAR) with significant contributions from L. Buja (NCAR).

A system for forecasting aerosols has been developed by members of the CGD Climate Modeling Section (William Collins, Philip Rasch, and Brian Eaton) and the Atmospheric Chemistry Division (Boris Khattatov, Jean-Francois Lamarque, and Charles Zender). The system, the first of its kind, combines a chemical transport model and an assimilation of satellite aerosol retrievals. The model simulates the three-dimensional distribution of atmospheric aerosols. The forecast system was used to plan aircraft missions during the recent Indian Ocean Experiment (INDOEX). The CGD scientists are extending the methodology to produce global aerosol analyses (See Figures, 34 K).  For more information, click here.

Recent analyses of the global carbon cycle suggest a significant role for terrestrial uptake of CO₂ in the overall budget. Analyses of atmospheric CO₂ have persistently suggested that this terrestrial uptake is largest in the Northern Hemisphere, and spatial analyses suggest that the U.S. may play a disproportionate role.

New Developments and Applications with the NCAR Regional Climate Model (RegCM) (Journal of Geophysical Research, 104, March 1999)

The following set of three related professional papers introduced further developments in an innovative approach for understanding how climate variability and change may influence various resource systems, including future food production in the United States and worldwide. The fundamental issue addressed by the papers concerns the development of high-resolution climate scenarios for use in impacts assessments. The need for more regional detail in climate scenarios has been pressing for more than a decade. The methodologies developed by this multidisciplinary team of researchers, led by Linda Mearns, will significantly advance capabilities for constructing such scenarios that assist nations in being better prepared for how to anticipate future weather and climate impacts on world food supplies. This special issue of the Journal of Geophysical Research describes several years of research efforts.

In the overview paper, Giorgi and Mearns discuss outstanding issues in state-of-the-art regional climate modeling (e.g., boundary conditions, model physics, two-way nesting, variable resolution approaches) and introduce the papers in the issue, which range in subject matter from the development of new physics for the model to various applications of the model, including its use for developing high spatial resolution climate scenarios for use in impacts assessments. These papers illustrate a wide range of applications over the United States, East Asia, Central Asia, and Eastern Africa. (Giorgi., F., and L.O. Mearns, 1999: Introduction to special section: Regional climate modeling revisited. Journal of Geophysical Research, 104(D6), 6335-6352.)

The second paper analyzes the difference in high resolution climate change scenarios formed using two different methods of regionalization: statistical downscaling and regional climate modeling. Boundary conditions from the same general circulation model (GCM), were used in both methods. The authors found that the two methods generated significantly different changes in climate when applied to a region of western Nebraska, including opposite directions of change in precipitation. This paper thus further elucidates very important uncertainties in the application of downscaling techniques. [comparison of downscaling methods] (Mearns, L.O., I. Bogardi, F. Giorgi, I. Matyasovszky, and M. Palecki, 1999: Comparison of climate change scenarios generated from regional climate models experiments and statistical downscaling. Journal of Geophysical Research, 104(D6), 6603-6621).

The third paper examines two different types of uncertainty in agricultural impacts assessments: the spatial scale of climate change scenarios, and the choice of crop model type. It is the first paper ever to demonstrate clearly the importance of these uncertainties. The authors developed a coarse-scale climate change scenario from a GCM used to drive the regional climate model and a high-resolution scenario generated from control and 2xCO2 results of the Regional Climate Model (RegCM2) for a region in the central Great Plains. They then applied the two different scenarios to two different crop model types (EPIC and CERES) for both corn and wheat. They found that substantial differences in percentage change in the simulated yields were calculated based both on the scale of the scenarios and the choice of crop model type. This paper convincingly demonstrates that these uncertainties in climate change impacts are complex and interactive. [regional climate change scenario] (Mearns, L.O., T. Mavromatis, and E. Tsvetsinskaya, 1999: Comparative responses of EPIC and CERES crop models to high and low spatial resolution climate change scenarios. Journal of Geophysical Research, 104(D6), 6623-6646).

Creeping Environmental Problems and Sustainable Development in the Aral Sea Basin (Cambridge University Press, 1999)

Multifaceted environmental degradation in the Aral Sea basin has been a touchstone for increasing public awareness of environmental change issues. The Aral crisis has been touted as a "quiet Chernobyl" and is one of the worst human-made environmental catastrophes of the twentieth century. Just a few decades ago, it was the fourth largest inland body of water in the world. Today, it has fallen to sixth place, and it continues to shrink.

This book, edited by Glantz, represents the culmination of five years of research begun in FY95 for the Water Unit of the UN Environment Programme (UNEP), with some initial support from the Water Unit. Twelve key environmental changes in the Aral Sea Basin were identified for assessment in terms of the thresholds of creeping environmental problems associated with them. Each member of a team of twelve Russian, Uzbek, Turkmen, and Kazak experts focused on one of these changes. Each expert had a decade or more of researching a specific environmental problem. Support was provided to them to prepare their chapters. Glantz initiated the development of a theoretical framework in a UNEP/NCAR workshop on Creeping Environmental Problems in 1994. This was organized to identify thresholds of problem awareness, crisis, and policy action for their respective problems. Glantz traveled to Russia several times on trips of opportunity during the FY95-99 period to discuss translation problems and to edit the manuscripts for clarity. The book presents these case studies as lessons to be learned for other areas undergoing creeping environmental change, especially for terminal inland seas. It provides an important multidisciplinary example of how to approach such environmental disasters for students and researchers of environmental studies, global change, political science, and history.

High Altitude Observatory

• Discovery of the first extrasolar planetary system around Upsilon Andromedae by a team from HAO, the University of California at San Francisco, and the Harvard-Smithsonian Center for Astrophysics. Three planets were detected in that system through their signature in the motion of the center of gravity as observed with precision spectroscopy developed at HAO in the context of solar and stellar seismology.

• Evidence for bright rings around sunspots from data gathered with the Precision Solar Photometric Telescope (PSPT) operated at HAO's Mauna Loa Observatory as part of NSF's Radiative Inputs from Sun to Earth (RISE) Program. The bright rings bear the signature of the redistribution of energy transported in and around big magnetic flux structures in the upper solar convection zone. The relation of such bright rings to the field distribution in and around sunspots was identified using data from the HAO/NSO Advanced Stokes Polarimeter (ASP) at Sacramento Peak Observatory.
  

Mesoscale and Microscale Meteorology

Surface Energy Bias in Climate Models (W. Pacific Warm Pool)

The cause of bias in the surface energy budget, and the attendant climate drift problem in coupled atmosphere-ocean general circulation models (GCMs), is a key uncertainty in climate modeling. Xiaoqing Wu (joint appointment with CGD) and Mitchell Moncrieff investigated this issue using a CRM (cloud-resolving model wherein convection and clouds are explicit), a single-column model (SCM) of the NCAR Community Climate Model (CCM, convection and clouds parameterized), and observations from the Tropical Ocean and Global Atmosphere Program Coupled Ocean-Atmosphere Response Exper-ment (TOGA COARE). They showed that top-of-atmosphere radiative fluxes and sur-face energy budgets derived from the CRM simultaneously agree with observations, while the SCM (run with the same prescribed forcing) is strongly biased. An accurate horizontal and vertical distribution of condensate and its effect on radiative transfer is crucial [see Figure 1 at bottom left]. This result shows convectively driven cloud systems must be param-eterized accurately before ocean-atmosphere coupling can be accurately realized, at least over the warm pool [see Figure 2 at bottom right].

Figure 1:
Left panel: 30-day evolution of 6-hourly vertical profiles of (a) cloud ice water mixing ratio (g kg-1) and (b) cloud liquid water mixing ratio (g kg-1) from the CRM. Right panel: Same as left panel but from the SCM. Click on image to view larger figure.

Figure 2:
The SST derived from the ocean model (dashed line) agreed very well with observations (solid line). On the other hand, a relatively poor prediction of SST was obtained when the ocean model was forced by surface conditions obtained from the single-column model (dotted line). Click on image to view larger figure.

Convection Initiation over Tropical Islands

Using a linear model and fully nonlinear numerical simulations, N. Andrew Crook (joint appointment with RAP) showed that radiative heating on the island scale is at least as important as sea breezes in initiating strong thunderstorms (known as Hectors) over the Tiwi Islands north of Darwin, Australia. In agreement with observations made during the Maritime Continent Thunderstorm Experiment (MCTEX), Figure 3 at the right shows the sea breezes from the north and south coastline converged to within 10 km of each other but did not collide, yet a Hector formed. This result raises the question of how convection over tropical islands should be initiated ('triggered') in parameterization schemes, and whether the sea-breeze collision mechanism is truly prevalent.

Figure 3:
Surface rainwater and velocity vector field at 1400 Local Time from a simulation of flow over the Tiwi Islands. An intense thunderstorm, locally known as a `Hector' has developed over the center of Melville Island (island to the east). Click on image above to view a larger version.

Research Applications Program

Mount Washington Icing Sensors Project (MWISP)

The detection of aircraft icing conditions (e.g., supercooled liquid water [SLW], freezing drizzle) is a major goal of the FAA-funded aircraft icing work at RAP. Current remote sensing systems operationally deployed such as the National Weather Service WSR-88D radars are not able to detect supercooled liquid water in the form of cloud droplets, nor are they able to tell whether radar backscatter is due to snow or freezing drizzle. A number of recently developed systems, however, show promise of being able to unambiguously detect supercooled liquid water and freezing drizzle. In order to evaluate their potential, the Mount Washington Icing Sensors Project was conducted during the month of April in the vicinity of Mt. Washington in New Hampshire, a region with significant amounts of icing and freezing drizzle. This was the first major field program ever conducted to test the ability of remote sensing devices to measure SLW and freezing drizzle. The program was organized and managed by RAP and included participants from government agencies, universities, and other research institutions.

Development and Implementation of Aviation Digital Data System (ADDS)

The National Weather Service’s Aviation Weather Center in Kansas City provides pilots and other aviation users Airmets (6 hour forecasts) and Sigmets (current conditions) of icing and turbulence every 4 hours. This information is provided in text form as a series of waypoints. While allowing rapid transmission of the information, it also requires aviation users to spend a great deal of time decoding the message. The Aviation Digital Data System (ADDS) has recently been developed by RAP and NOAA/FSL to provide the above weather information, as well as experimental weather products developed by RAP, in a user-friendly graphical manner over the Internet. The system was transferred to the Aviation Weather Center in Kansas City in 1999, and it has proven to be very robust and extremely popular with users. RAP’s work in developing this system recently won NCAR’s Outstanding Scientific and Technological Accomplishment Award.

Transfer of Weather Support to Deicing Decision Making (WSDDM) System to ARINC

The Weather Support to Deicing Decision Making (WSDDM) system is designed to provide airlines and airports current weather information and nowcasts of snowfall. A key aspect to the WSDDM system is the use of snow gauges to measure the liquid equivalent snowfall rate. Research conducted at RAP has shown that the current operationally available snowfall intensity based on visibility can be misleading to deicing operators in many instances. The WSDDM system overcomes this problem by providing real-time measurements and nowcasts of liquid equivalent snowfall rates. This technology was successfully transferred to ARINC during the past year, and is currently available commercially to airlines and airports. It is currently operational at LaGuardia, JFK, and Newark airports in the New York City area. The system was awarded the U.S. Government’s Technology Leadership Award in December 1999.

Scientific Computing Division

New computational hardware roadmap

One of SCD's highlights for FY1999 was developing a new computational hardware roadmap and taking the first steps on the path it defines. This is a significant step forward in our plan to identify, acquire, and operate a new generation of computing hardware architectures for NCAR and our university community.

This roadmap and our implementation of it are so significant because NCAR and SCD must adapt to major changes in both the technologies and the market forces now driving the development and availability of computing engines in the United States. This change in supercomputing fundamentally affects how scientists perform numerical simulations for geosciences research, and it has profound ramifications for model design and production.

SCD must provide platforms that allow the science to adjust to these new computing engines in a way that advances scientific output and avoids disruptions or delays. SCD's computational hardware roadmap presents options that could allow SCD to provide Teraflop computing capabilities in FY2000. This roadmap is fundamental to ensuring that NCAR's scientific research community will have access to the most potent computing resources available.

Acquisition, installation, and acceptance of blackforest

The acquisition and installation of the IBM RS/6000 SP computing system, "blackforest." This is a significant accomplishment for the division because it represents the culmination of a process of identifying the best next generation supercomputing system for NCAR.

SCD has a sterling reputation for testing the most advanced computing engines and aims to acquire the very best in computing technology to meet the demanding needs of the scientists we serve, both now and into the future. Our evolving partnership with IBM is an important ingredient for increasing the computing power supporting that science.

Educational Activity Highlights

Twenty-four students from the U.S. and Puerto Rico participated in the fourth summer of Significant Opportunities in Atmospheric Research and Science (SOARSÔ). These SOARS protégés worked with scientific mentors from seven NCAR divisions, Argonne National Laboratory, Goddard Space Flight Center, the Universidad Nacional Autónoma de México, and the University of Colorado (Aerospace Engineering Sciences, Cooperative Institute for Research in Environmental Sciences, Laboratory for Atmospheric and Space Physics).

LEARN: Atmospheric Science Explorers, a four-year project that provides atmospheric science training for rural Colorado teachers completed its third year of funding with intensive training for 38 teachers at NCAR during June 1999. An additional 162 teachers and 915 students participated in in-district training in the rural areas during the 1998-99 academic year.