Discuss the following in the context of global precipitation distribution i. Tropical Precipitation ii. Mid-latitude precipitation iii. Low precipitation areas iv. Rain days

i. Tropical precipitation
Precipitation in much of the tropics is associated with convective activity. Strong vertical motions occur in a fluctuating band near the equator. This release the abundant water vapour, which creates a regime of intense, short-lived storms from cumulus clouds. Rainfall rates in excess of 100 mm per hour are not uncommon. Although the location of the storms is partly controlled by local topographic features, storms tend to recur sporadically, so that precipitation does not occur at a particular place every day even though there may be a storm in the area each day.
More widespread uplift is associated with monsoonal circulations. Such circulations are particularly well developed over tropical Asia. Although this is a strongly seasonal precipitation regime, the effects of convective uplift, dynamical uplift and topographic forcing combine to produce high annual rainfall totals. Locally rainfall rates may be very high but generally the monsoonal condition is characterized by longer lasting, less intense precipitation.

ii. Mid- latitude precipitation
In mid-latitude much of the precipitation production is associated with depressions and fronts.
The result is widespread uplift giving extended periods of gentle rain over a broad area. Rainfall rates vary greatly, although 1-2 mm per hour, which is regarded as a typical value. The intensity is partly controlled by the amount of water vapour available, which in turn depends on the source of the air, which is being uplifted. Air derived directly from the subtropical oceans, where evaporation rates are high is likely to lead to higher precipitation rates. If the source is the tropical deserts, the air is likely to be much drier and it is not uncommon in these conditions for dust and sand particles to form the condensation nuclei and hence to be deposited in large quantities with the rain.
Convective activity in the mid-latitudes is primarily a summer phenomena. It can be intense, but is usually less regular, than in the tropics.

iii. Low precipitation areas
The regions of low precipitation in the sub-tropics result mainly from a lack of mechanisms for creating uplift and bringing the air to saturation. Certainly over the oceans and to a large extent over the land deserts as well, there is lack of moisture in the atmosphere in the atmosphere. In contrast, over the Polar Regions the low precipitation totals are as much associated with a lack of atmospheric uplift mechanisms.

iv. Rain days
The spatial distribution of rainfall can also be viewed in terms of the number of rain days per year. A rainy day is usually starting at 0900 GMT, during which 0.2 mm or more of precipitation falls. The climatic average of rain days varies from over 180 per year in humid coastal regions to less than one per annum in very arid regions. In general there is a close relationship between the number of rain days and the total precipitation. However, seasonality can influence the relationship between rainfall totals and rain day numbers. Places that experience distinct wet and dry seasons may have high rainfall
totals but few numbers of rain days. The relationship between rainfall totals and rain days therefore depends strongly on the climatic regime and on the nature of the precipitation producing systems. For many purposes the total rainfall in a given period is the most useful measure of precipitation, but in some cases the number of rain days is more appropriate.

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francis1897 answered the question on October 5, 2022 at 05:41