by Robert Van Buskirk, Ph.D.
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Meteorological models are used to
estimate the effects of complex geography for
mapping Eritrean climate and resources. Eritrea has a complex
geography that consistes of steep mountain slopes, topographically
induced rainfall, and complex land/sea interactions. These effects
can result in rapid small-scale variations in climate, vegetation,
land use, populations, and socio-economic activity.
Through development of a national Eritrean climate model we are mapping the daily and monthly variations in climate to a temporal resolution less than one hour, and a spacial resolution of less than four kilometers. This is achieved through the development of computer models that account for the flows of heat, momentum, air, and water vapor over the South Red Sea and through the Eritrean Highlands. |
A national climatological and meteorological model is an essential piece of informational infrastructure for Eritrea's national development. With the increasing power of personal computers it is now possible to run fairly sophisticated weather and climate simulations on computers that cost only a couple of thousand U.S. dollars. At the same time climate data collection is difficult and slow in Eritrea. One climatological data collection station can cost as much as $10,000 and with steep slopes and complex topography it can be difficult to generalize the measurements of one station more than a few kilometers. A climate and meteorological model can perform such geographic data extrapolations with enhanced detail and precision compared to less sophisticated methods.
Climate models can account for solar heating effects in complex topography, they can account for winds and temperature differences caused altitude, differential heating, and green vegetation. They can also account of atmospheric water transport and attempt the calculation of rainfall patterns and cloud patterns. But they still have difficulty calculating the detailed smaller-scale dynamics of atmospheric instabilities. In spite of many of the computational challenges of meteorological modeling, rapid progress is being made in this field.
Our initial modeling approach is to use a Force-Restore, Advection/Diffusion Heat and Momentum Accounting approach in our customized model development. In this approach, we first define an approximate equilibrium state for the atmosphere, along with equilibrium restoration times for different components of the atmospheric dynamics. We use this approach because of the promise it has already shown in one-dimensional climate modeling for Eritrean meteorological data. Furthermore the approach allows us to specify the global climate effects and inputs in terms of the atmospheric equilibrium state, while it also provides a very stable and robust framework for the rest of the computation.
The equilibrium vertical profile of the atmosphere can be estimated by looking at nearby upper air sounding data. The two sounding stations that we have found closest to Eritrea with Internet accessible data include:
Depending on the exact period, daily or twice-daily data may be available with varying vertical resolution.
In the simulations that we will do, we wish to estimate the actual weather and atmospheric dynamics with a minimum of error (where that error is usually measured as a root mean square deviation from the observed meteorological parameters). We therefore want to optimize our model to the typical or average conditions and then model deviations from the average or typical.
Here we difine typical conditions as a specific measured set of atmospheric parameters and conditions that are 'close' to conditions that are observed quite often. Typical conditions are common conditions. Note that given the complex interactions between different physical parameters in the atmosphere, it usually better to model typical conditions rather than average. Average conditions will generally not be consistent the with physical laws of atmospheric dynamics whereas typical conditions will be.