Catabatic wind is a wind that originates from high mountains whose temperature is very low. Its etymological origin is the Greek word Catabasis, which means landing. That is why the other name of this wind is autumn wind. The temperature of the catabolic wind depends on the temperature of the source area and the amount of landing. Wind speeds are generally 5-10 knots.

Mountain wind is a cool, high-density wind that blows from the heights to the stations at the foot of the hills. As it happens, the rare atmosphere of the high mountains returns to the atmosphere on a dry and clear night much faster than the plains. The slopes of the mountain, under the influence of cooling radiation, cool down quickly, and as a result, the air becomes much colder in close contact with the slopes of the mountains. As it cools, it becomes denser and heavier, and along the slopes of the mountains, under the influence of gravity, begins to glide at a normal speed in the range of 5-10 knots or 18-9 km / h. It reaches a deep valley near or at the foot of a plateau in the early morning hours and cools even in the relatively warm months.

Here we discuss the typical catatonic wind scenario in Pakistan considering the temperatures of Hill Murray Station, Islamabad Mountain Station and Lahore Plain Station.

Mori Scenario Islamabad

In the cold, dry autumn months, the barley in Murray is usually dry at night. The sky is perfectly clear and the humidity is very low. At sunset, due to the clear atmosphere and dry weather, the slopes of the Murray Mountains cool rapidly due to the re-radiation of heat accumulated during the day to the atmosphere. As the mountain slopes get colder, the air cools in close contact with it. It is now known that temperature is inversely related to air density. Therefore, the air becomes dense and heavy and descends to the foot of the hills at an average speed of 5-10 knots under the influence of gravity. It arrives in Islamabad in the early morning hours and creates a cold there, otherwise there would be no phenomenon. A comparison of the following temperatures further illustrates this point.

Let’s compare the typical late October temperatures in Murray (hill station), Islamabad (plateau station near the hills) and Lahore (a simple station located very far from the hills). As described above, the conditions required to create a fully catabolic effect are a smooth atmosphere with little or no wind at the source site and low relative humidity. Incidentally, all of these factors are available in Murree from late October to early November. The temperature in Murray drops sharply at night and the air gets colder along the slopes and lands towards Islamabad, cooling it by more than 5-6 degrees compared to the plain stations. Occasionally, the minimum temperature in Islamabad drops below the minimum Murree, the site of the katabatic wind source. The usual time of day and minimum night in Murray, Islamabad and Lahore for late October are as follows:

Murray 19 8

Islamabad 29 7

Lahore 31 15

Note the effect of catabatic wind on the minimum temperature of Islamabad. 8 ° C is colder than Lahore, although up to 10 ° C is warmer than Murray. Also pay attention to the daily temperature range in Islamabad, which is 22 degrees Celsius. This is usually in Katabatic areas.

In short, Katabatic wind is a cold and dense wind that dramatically changes the temperature regime from which it descends.



Source by Waqar Awan