The Mesoclimate Subproject

Objectives:

The objective of the "mesoclimate subproject" of SWAP is to investigate the relationship between changing climate and vegetation on the 'mesoscale', i.e. scales from 5 to 500 km, using conventional data, satellite data and simple models. The attainment of this objective requires solving or avoiding the following problems:

1. The network of conventional climate stations (at least those whose data is available internationally) has variable spacing, with an average spacing of about 100 km. Climate records contain errors and missing data. Satellite data is influenced by instrument and orbit drift as well as clouds, haze, and atmospheric absorption.

2. The region has an arid climate, with precipitation and evaporation being the most critical factors for vegetation. The precipitation varies considerably from year to year, and has a mesoscale pattern controlled by localized moisture sources and mountain barriers.

3. Areas with natural "climax" types and amounts of vegetation are relatively rare in the SWAP region due to extensive: deforestation, overgrazing, irrigated agriculture, and dryland agriculture.

Strategy:

• The construction of regional scale, flexible format, climatology of SWAP region using conventional station data and the new NCEP/NCAR Reanalysis meteorology data sets. This climatology will include: improved 5 km terrain dataset, average airflow trajectories from sources of water vapor, precipitation seasonality diagrams, potential evaporation patterns, 40-year history of interannual variation, reference el Nino, upslope wind and baroclinicity time series.

• The design and verification of a "physical interpolation" scheme for determining climate on the mesoscale. This interpolation scheme will include a lapse rate correction for the effect of terrain on temperature and possibly a mountain barrier correction for precipitation. The lapse rate correction will be tested using a statistical method relating lapse rate to interstation distance, a local satellite lapse rate analysis using AVHRR Channel 5, a regional comparison of satellite derived surface temperature with interpolated station temperature and the correlation of interpolated climate data with satellite observed vegetation patterns. Click here to link to SWAP Climate Runs.

  Interpolated Air Temperature with Lapse Rate Correction

• The identification and description, using objective methods, of disturbed areas of the landscape. These methods include AVHRR leafout/harvest indices, dry season NDVI, temporal NDVI classification. Fourier NDVI analysis, high resolution Landsat image analysis and ground truth.

  Unsupervised Classification of the SWAP Area

• The estimation and explanation of the interannual variability of vegetation in natural and disturbed areas. Evaluate the role of climate in causing these vegetation changes.

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Last modified 19 Jan 1998.