Summer rain stocks dams

Summer rain stocks dams

Subject : Geography

Context : Although the monsoon has not covered the whole country yet, summer cyclones and thunderstorms have left reservoirs with more water than their average at this stage.

Concept :

• The summer of 2021 saw unusually cool day temperatures over most regions. This could have led to below-average evaporation from surface water stocks across the core heat zones, where heatwaves and high day temperatures are common during March-June.
• The cooler summer was also due to frequent thunderstorms that brought rainfall spells at many places between March and May.
• During the second and third weeks of May, Cyclones Tauktae and Yaas caused widespread rainfall over two-thirds of the country.
• The all-India weekly rainfall during May 12-19 and May 20-26 was, respectively, 127% and 94% above the Long Period Average.

Long Period Average (LPA):

• It is the average rainfall recorded during the months from June to September, calculated during the 50-year period, and is kept as a benchmark while forecasting the quantitative rainfall for the monsoon season every year.
• IMD maintains an independent LPA for every homogeneous region of the country, which ranges from 71.6 cm to 143.83 cm.

Thunderstorms

• Thunderstorms and tornadoes are severe local storms. They are of short duration, occurring over a small area but are violent.
• Thunderstorm is a storm with thunder and lightning and typically also heavy rain or hail.
• Thunderstorms mostly occur on ground where the temperature is high. Thunderstorms are less frequent on water bodies due to low temperature.

Motion of a thunderstorm

• Path of a thunderstorm is erratic. Motion is primarily due to interactions of its updrafts and downdrafts.
• The speed of isolated storms is typically about 20 km (12 miles) per hour, but some storms move much faster.
• In extreme circumstances, a supercell storm may move 65 to 80 km (about 40 to 50 miles) per hour.

Downbursts

• Downdrafts are referred to as macrobursts or microbursts.
• Macroburst is more than 4 km in diameter and can produce winds as high as 60 metres per second, or 215 km per hour.
• A microburst is smaller in dimension but produces winds as high as 75 metres per second, or 270 km per hour
• They are seriously hazardous to aircrafts, especially during takeoffs and landings.