Status of Remote Sensing of the Troposphere

Abstract

This paper attempts to summarize the status of remote sensing of the troposphere. It opens with a statement of the need for remote sensing and identifies the potential advantages inherent to such techniques. The main material is in the form of a series of tables which identify the stage of development of each method (acoustic, radio, or optical) for the measurement of the different meteorological parameters relevant to the troposphere. The tables are used to differentiate between those capabilities which as yet are limited to the boundary layer, and those applicable to the full height range of the troposphere; and also between those techniques which are limited to clear air as opposed to those which can operate in the presence of cloud particles and/or precipitation. Examples of the current capabilities of various active and passive acoustic, optical, and radio remote sensing systems are presented in the form of figures, primarily from the work of the Wave Propagation Laboratory. The role of remote sensing in the troposphereAs the size and complexity of our society increases, the number and complexity of its interactions with our atmospheric environment grows. As a result, the economic costs to commerce, transport, communications, and agriculture of natural disasters such as blizzards, ice storms, hurricanes, tornadoes, floods, droughts, etc., increase year by year. This growing sensitivity to weather conditions has, of course, led to a greatly expanded need for atmospheric information and forecasts of many different types, for many different purposes.The attainable quality and scope of an environmental information or forecasting service is determined by the nature of the observational data set on which it is based -and especially by the density in time and space of the relevant observations. Thus, the present meteorological observing system of ground-released radiosondes and satellite measurements is well matched to synoptic-scale weather patterns, i.e., to space scales of the order 1000 km and time scales (at one location) of the order one or two days. But recent analyses of national needs for improved weather services show that these needs lie primarily in the area of short-term local weather forecasts, e.g., forecasts for a local area 1 to 100 km in size, for time periods ranging from 0 to 6 hours. These improved short-term local weather forecasts inevitably will require a much denser array of meteorological data than is currently available from the present observational networks. The required increase in space-time density of relevant observations is huge-at least four orders of magnitude relative to the twice-per-day, 500-km horizontal spacing of the upper air radiosonde observing system. Cost estimates indicate that it is totally impracticable to achieve this desired increase in density of observations by mere expansion of the existing radiosonde network. Satellite remote sensing of meteorological conditions is, of course, already playing a very important role; however, because of the great need f...

Doppler Radar Probing of the Clear Atmosphere

“…The rawinsonde provides only sparse data (every 12 h on an ~500 km grid in populated areas) at considerable expense in expendables. Little (1972) has enumerated the advantages of remote sensing for routinely observing the atmosphere. He points out the inadequacy of rawinsondes for obtaining the dense set of observations required for short-range forecasting.…”

Remote Sensing for Air Pollution Meteorology

“…Recent publications (Derr and Little, 1970;Little, 1972Little, , 1973Derr, 1972) have dealt with the status of groundbased remote sensing. We shall borrow from these reports, which detail the many advantages of remote sensing, updating where necessary to give a brief overview of the field.…”

“…The in situ sensor is capable of, at best, a one dimensional measurement (recognizing that the atmosphere advects the measured variable past the sensor) while remote sensors have the powerful capability of multidimensional observations. This point is treated by Little (1972) in his listing of the range of measurements that are possible, going from a simple line integral to the determination of flux.…”