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MODELING GLOBAL AND REGIONAL CLIMATE
PI: Georgiy Stenchikov Co-PI: Alan Robock
Agency: 1 Department of
Environmental Sciences, Title: Stratospheric Aerosol Data Assimilation for Climate Studies
Abstract:
The intellectual merit of
the proposed activity Co-PI: None Agency: Supported directly by CEP Title: A Statewide Hydrologic Model Abstract: We are in the process of constructing a hydrologic model that integrates surface water and groundwater processes for the state of New Jersey, using USGS MODFLOW and its Streamflow Routing Package, within the GMS4.0 modeling environment. The model will take RAMS estimated surface runoff and groundwater recharge, and produce stream flow rate and groundwater level. The model will be used to assess the effect of climate and landuse change on water resources of the state. It will also serve as a physical framework for addressing a wide range of chemical and biological and social issues related to our environment. The first stage of the model is complete. For more information please contact yingfan@rci.rutgers.edu.
PI: Robock Co-PI: None Agency: NOAA Title: Volcanic Forcing of Climate over the Past 2000 Years: An Improved Ice-Core-Based Index for Climate Abstract: To evaluate the relative impacts of human pollution and land surface modifications on climate, natural causes of climate change must also be considered. The only way to test if natural variability is correctly captured by climate models is by looking back in time beyond the 20th century, when climate variations were clearly dominated by, if not exclusively caused by, natural forcing. This will also give us more confidence in the sensitivity of the same models used for simulating the future response to anthropogenic greenhouse gases, aerosols, and land surface changes. The two most important natural causes of climate change are volcanic eruptions and solar irradiance variations. We now have a unique opportunity to improve our knowledge of the volcanic forcing record for the past several millennia with the agreement of the group at the University of Copenhagen to allow us to use the records of several ice cores previously drilled in Greenland and never before used for estimating atmospheric perturbations from past volcanism. Several other ice core groups have agreed to support our effort with published and previously unpublished high resolution data. These new records will be combined with others that have become available in the past decade to produce an improved record of the volcanic loading of the atmosphere. Because of large spatial variability of volcanic deposition on ice sheets, it is important to include a large number of records in the construction of past volcanic forcing. An extensive list of cores prevents errors inherent in reconstructions based on a single or small number of cores. This will produce more accuracy both in detection of events and quantifying atmospheric loading. The ice core data will be combined with a new understanding of stratospheric transport of volcanic aerosols to produce a forcing data set as a function of month and latitude. The new forcing will then be used in climate model simulations to better determine the volcanic component of past climate change.
PI: Robock Co-PI: Stenchikov and Thordarson Agency: NSF Title: Cooperative Research on Climate Effects of the 1783-1784 Laki Volcanic Eruption Abstract: The 1783-84 AD Laki flood lava eruption in Iceland emitted a total of about 122 megatons (Mt) of SO2 into the atmosphere and maintained a sulfuric aerosol plume that hung over the Northern Hemisphere for more than 5 months. The eruption columns extended to altitudes of 9-13 km and released about 98 Mt of SO2 into the stratosphere, which reacted with water vapor to produce about 200 Mt of H2SO4 aerosols (assuming a 100% conversion rate). The Laki aerosol cloud was delivered from upper troposphere/lower stratosphere altitudes to the surface by subsiding air masses within anticyclones. By this process, 175 Mt of H2SO4 aerosols were removed from the atmosphere in the summer and fall of 1783. The remaining 25 Mt stayed aloft for more than one year, producing a maximum optical depth in the visible of about 0.7. This lower stratospheric component is likely to have produced long-lasting atmospheric perturbations, whereas the lower tropospheric haze caused extreme volcanic pollution that affected many regions of the Northern Hemisphere in the summer and fall 1783. The Northern Hemisphere summer of 1783 was characterized by extreme and unusual weather, including record warm temperatures in western Europe, and the following winter was one of the most severe winters on record both in Europe and North America. The annual average, hemispheric cooling that followed the Laki eruption was as on the order of -1.3°C and lasted for 2-3 years. If such an eruption were to occur today, the most likely immediate consequences would be a complete halting of all air traffic over large portions of the Northern Hemisphere. We are working to model the effects of this eruption to enable us to understand the mechanisms (chemical, radiative, and dynamic) that produced the response in the climate system. This will produce a system that will be able to predict the response to similar eruptions in the future. We are assembling observations of the emission and distribution of the Laki aerosols and of the meteorology during 1783 and 1784 in a quantitative form for use in forcing and validating simulations. We will run global climate models forced with the aerosol and gas data set and calculate the global climate response, using many ensemble members to address the chaotic nature of atmospheric circulation. We will also run the model with assimilated surface pressure observations to simulate the observed aerosol distribution and temperature for the summer over Europe, to separate radiative from dynamic effects. Our previous work has helped to explain the winter warming phenomenon following large tropical eruptions. Here we will investigate the atmospheric dynamic and radiative responses that produce summer warming and winter cooling from high latitude eruptions.
PI: Robock Co-PI: Stenchikov, Miguez-Macho,Y.-F. Reinfelder Agency: NJDEP Title: Impacts of Climate Change on NJ Water Resources Abstract: This project seeks to understand the impact of future climate change on the citizens of New Jersey, particularly on the availability of water resources. We have compared the simulations of eight state-of-the-art global general circulation climate models for the current climate to observations and examined simulations of drought frequency for the northeast United States from the models for the period 1901 to 2050. We found that while the models behave quite differently from each other, the ensemble averages of the model simulations showed decreases in the frequencies of droughts in the future. We have recently completed detailed evaluations of our high resolution model, the Regional Atmospheric Modeling System (RAMS). This model, which has proven very useful for short-term simulations of convection and land surface interactions, had never before been used for longer term climate downscaling. Our first attempts found several aspects of RAMS performance that degraded the precipitation simulations, and precipitation is the most sensitive indicator of model performance. By improving numerical schemes and convective and turbulence parameterizations of the model, implementing a new spectral nudging technique, and evaluating its performance with extensive testing of its ability to simulate the current climate, we now have a model that is ready for use in downscaling the low resolution climate model projections for the future and producing detailed input to a hydrology model. We are now beginning to conduct RAMS simulations of the detailed response of precipitation patterns and other weather elements to future climate. These calculations will involve dealing with issues including model resolution for an inner grid over New Jersey and the best method of coupling global climate model simulations of the future climate to RAMS. These simulations will take into account the results described above to choose which models and which variables to analyze. In parallel, with other funding, Dr. Ying Fan Reinfelder has developed a model of streamflow and water table depths for the entire state of New Jersey, taking into consideration the detailed geology of the state. This model requires input of precipitation, atmospheric temperature, downward solar radiation, and other variables on a fine grid and produces time series of streamflow, soil moisture, and water table depths on this same fine grid. It is now ready to be used. We will produce these inputs from the RAMS simulations and work with Dr. Reinfelder to run the hydrology model and analyze the results.
PI: Stenchikov Co-PI: Shnaydman Agency: Supported directly by CEP Title: Diagnostics and Improvement of the Turbulence Parameterization in the Regional Atmospheric Modeling System (RAMS) Abstract: We found that the well known Mellor-Yamada turbulence parameterization used in RAMS for simulations with medium and relatively fine spatial resolution (when vertical spacing is still much less than horizontal) produces erroneously large turbulence mixing above planetary boundary layer. We thoroughly tested the model conducting mesoscale and cloud-resolving calculations and found that the reason for this deficiency is related to the incorrect definition for mixing length used by Mellor and Yamada that is not applicable above boundary layer. We modified this relation using approach proposed by Helfand and Labraga. The preliminary experiments with the improved turbulence parameterization give promising results.
PI: Weaver Co-PI: None Agency: NASA Title: Evaluating the Effects of Historical Land Cover change on New Jersey Weather and Climate Abstract: The human conversion of the land surface over the last few centuries has resulted in a significant modification of its biophysical properties (Ramankutty and Foley 1999). Modification of land cover, its spatial heterogeneity as well as its mean characteristics, drives changes in the land-atmosphere fluxes of heat, moisture, and momentum. These changes in turn impact weather and climate through influences on atmospheric dynamics, thermodynamics, convection, clouds, and rainfall (see Pielke 2001 for a review). A number of recent studies have suggested that impacts of land cover change on large-scale climate could be comparable to those associated with changing atmospheric composition. Links between the patterns of land cover change, the processes driving it, and its impacts on the weather and climate are particularly strong at scales much finer than global. For example, studies have begun to demonstrate the significant influence of anthropogenic surface perturbations on mesoscale atmospheric processes (e.g., see Weaver and Avissar 2001). Quantifying the types of land cover change and the subsequent responses of the coupled land-atmosphere system that can occur at regional and local scales is critical, as these are the scales of ecosystems and human communities. Many important issues are not yet well understood, however, and attacking this problem is the overarching theme of the work described here. Our particular focus is land cover change in New Jersey and surrounding regions during the last century. In the northeastern U.S. in general, extensive urban and industrial development, along with the displacement of agriculture, has produced dramatic changes in land cover. We wish to understand in what ways, and to what extent, these land-surface changes have altered the climate of this region. This question is relevant from a number of perspectives. For example, separating the effects of land cover change will assist in distinguishing the regional fingerprints of a possible global climate change signal. In addition, landscape change driven by population growth and economic development is expected to continue, and even accelerate, into the future. An evaluation of how historical land cover change may have modified weather and climate is one prerequisite for understanding and predicting the broader impacts of future changes. Specifically, we are attempting to answer the following questions:
We have selected New Jersey as the primary domain of interest because it is the only state in the country where a spatially accurate dataset of documented 19th-century land cover is available at a resolution comparable to that of satellite imagery. Our main tools for investigating the scientific questions posed above are (a) this historical dataset, (b) the USGS National Land Cover Dataset (NLCD), based on Landsat Thematic Mapper imagery, and (c) a state-of-the-art mesoscale numerical model, the Regional Atmospheric Modeling System (RAMS). Our strategy is to run RAMS at high resolution, forced at the lower boundary with these representations of historical and present-day land cover (and, eventually, scenarios of future land cover), and to quantify the differences between these experiments.
Co-PI: None Agency: NASA Title: Modeling of regional-to-global aerosol effect on climate and photochemistry Abstract:
In this project we will use the NASA Goddard Space Flight Center
(GSFC) Data Assimilation Office (DAO) GEOS Stretched-Grid GCM (SG-GCM) and
stretched-grid Data Assimilation System (SG-DAS) for producing
meteorological fields with high regional resolution for tracer transport
simulations and calculations of radiative forcing and climate response.
These systems are consistent with our stretched-grid University of
Maryland Chemical Transport Model (UMD-CTM) employed in this study. We
will make use of the latest versions of the GEOS GCM and DAS identified as
GEOS-3 and GEOS-4.
The focus of this project is on computation of export fluxes for
trace gases and aerosols from the continents especially North American
outflow. We will use a stretched-grid configuration with fine resolution
over central and eastern North America and the Western Atlantic.
Simulations will be conducted for the summers of 5 years between 1990 and
2000. The simulated periods will correspond to the summers in which
previous field programs (ABLE-3B, NARE, TARFOX) were conducted. The model
will also be run for Spring 1996 (NARE, AEROCE) and Fall 1997 (NARE,
SONEX). All of these aircraft data will be used to evaluate the model.
The summer of 2000 (with MOPITT CO available) will be one of the five
summers simulated. Other satellite data that will be used to evaluate the
model will be TOMS tropospheric ozone, TOMS aerosol index, GOME NO2, AVHRR
AOD, and MODIS aerosol products. Interannual variations in export flux
associated with variations in North American biomass burning will be
examined. |