Photogrammetry from Aircraft Side Camera Movies: Winter MONEX

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  • 1 Department of Environmental Science, University of Virginia, Charlottesville 22903
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Abstract

A new method is described for photogrammetry of clouds from aircraft side camera movies, to take into account cloud motion. In extreme circumstances of measurement, this leads to improvements of 500 m in cloud height. General use of the method is desirable when cloud measurements are related to other data.

On 10 December 1978 over the South China Sea, cumulus fractus were of depth ∼0.2 km, and updrafts were of width ∼0.25 km. For humilis the corresponding numbers were 0.7 and 0.4 km. Mediocris with tops at height (z) 2.2 km had updrafts of width (w) ∼1.3 km. Updrafts in congestus towers increased with height, with dw/dz ∼0.17, a figure similar to that found for day 245 of the GARP Atlantic Tropical Experiment.

Cloud number densities on 10 December varied over an order of magnitude over distances of 100 km, even in circumstances relatively uniform on the large scale. Order of magnitude estimates of percent area coverage by updrafts yield values up to 10% for fractus and humilis combined, up to a few percent for mediocris, and less than 1% for congestus in the mid-troposphere. An area measuring 1° latitude × 2° longitude was found to contain nine cumulonimbi, yielding ≈0.1% coverage by updrafts in the mid-troposphere.

Abstract

A new method is described for photogrammetry of clouds from aircraft side camera movies, to take into account cloud motion. In extreme circumstances of measurement, this leads to improvements of 500 m in cloud height. General use of the method is desirable when cloud measurements are related to other data.

On 10 December 1978 over the South China Sea, cumulus fractus were of depth ∼0.2 km, and updrafts were of width ∼0.25 km. For humilis the corresponding numbers were 0.7 and 0.4 km. Mediocris with tops at height (z) 2.2 km had updrafts of width (w) ∼1.3 km. Updrafts in congestus towers increased with height, with dw/dz ∼0.17, a figure similar to that found for day 245 of the GARP Atlantic Tropical Experiment.

Cloud number densities on 10 December varied over an order of magnitude over distances of 100 km, even in circumstances relatively uniform on the large scale. Order of magnitude estimates of percent area coverage by updrafts yield values up to 10% for fractus and humilis combined, up to a few percent for mediocris, and less than 1% for congestus in the mid-troposphere. An area measuring 1° latitude × 2° longitude was found to contain nine cumulonimbi, yielding ≈0.1% coverage by updrafts in the mid-troposphere.

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