: t Western Depression (| Convectional Rainfall or Rainfall through Thunderstorm: (April . Summer monsoon are called south-west monsoon while winter monsoon are called north- cast Primary winds originate from the Bay of Bengal. These winds cross Bangladesh and India and reach northern and eastern parts of Pakistan ‘mainly North Easter areas of the country ‘These rain bearing winds rise to a significant height due to low air pressure. They get chilled and condensed to cause heavy rainfall from July to September Secondary winds originate from Arabian Sea These are weak winds and bring some rain to the southern Punjab and Sindh Dec - March) ‘The winds causing rainfall during winters originate from the Mediterranean Sea. ter originating from the Mediterranean Sea they move to the east. On their way to Pakistan the western depressions cause rainfall over Turkey, Middle East counties, Iraq, Iran Afghanistan and then Pakistan. Most of the precipitation falls on its way to Pakistan, receives very little rainfall during winters, The amount of rainfall during winters is lower than the amount of rainfall during summer. The western depression causes rainfall at lower altitude and snow fall at higher altitude areas. Northern, North western.and western side of Pakistan receive their winter rainfall through the western depression t Murree, Swat, Gilgit, Hunza, Mardan, Peshawar, Quetta, Ziarat etc are some of the areas those receive winter rainfall through the western depression. June, Oct-Mid Dec) Unlike monsoon and western depression, convectional rainfall is experienced by the locally evaporated winds Through local evaporation & transpiration the water molecules go up to the atmosphere and after condensation, these molecules get the form of clouds and these clouds cause rainfall at the nearby places. Convectional Currents are associated with the windstorm or thunderstorm and cause uprooting of trees and destruction as well Convectional rainfall can be experienced at any place in Pakistan, particularly North and North western areas of Pakistan. Rawalpindi and Peshawar receive some rainfall in early summer caused by convectional currents. Relief rainfall: [ Leeward Side Oe Dry ir j a! is warmod Ty onwot 44 precipitation g Air cools and Rain shadow condenses desert (ee Mean tkan An TIUE iRR is mainly confined to RR Ie main the northern mountainous areas, where there is the largest forest + Due to excessive rate of - and mote and more feast transpiration more water molecules go up into the atmosph: 3d more and more water gets back othe ground i he form of rafal pnere The wae }Ountains receives more relief rainfall than the leeward side of the Tropical cyclones: * TC brings a few h : gs jours of v : They Sera peer Beaty) rainfall with destructive winds to the coastal areas. s) The) iat Gi rainfall is totally unreliable. : a iting Pal many are diverted towards Indian coast. living near 2 istan coast cause serious problems for fishing community and people . cutia Near Coast and futher ila areas of lower Sindh ~ stock are destroyed and power and communication lines are disrupted How tropical storms are formed High humidity ly and ocean temperatures of over 26°C are major contributing factors ‘As pressure in the central column ater sapermes tonite, _Agelumnetionpemeni Beau Suagerass ome,, ealummotiouprestire,, fneetenne form around the column of the wind around it increases air, forming clouds Effectiveness of rainfall Rainfall in Pakistan is main| Monsoon winds bring rain in sul distribution. «As temperatures are high in summers therefore, there is more evapo precipitation. Monsoon comes in heavy showers and is not useful for farmers. Winter rainfall is more effective and useful for farmers as it comes in light showers. continue for several days ly from Monsoon and ‘Western Depressions . immers which are unreliable in terms of amount, timing anc . -transpiration the: Floods water that submerges land that is usually dry. In the sense of flowing A flood is an overflow of the word may also be applied to the inflow of the tide. Flooding may occur as an overflow of water from water bodies, such as a river, lake, Cr ocean, in whic the water overtops or breaks levees, resulting in some of that water escaping its usual bou datMelting of snow from mountains in summer Heavy rainfall especially monsoon Lack of high embankments of rivers to control water No reservoirs to store and control the flow of water. Deforestation in the foothills of the Mountains sIndia opens the syphon flowing water in three rivers Benefits More alluvium flow can result in fertility of soil More water can be used for producing HEP Water can help in the irrigation for cultivation. More fish can flow in rivers to the delta of the sea. High level of reproduction, breeding of fish in fresh water areas Recharge the ground water supply. Damages Residential areas will cut off from shops and services. . Destruction of crops. Houses can be damaged. Epidemics break out causing people to be sick The roads and railway tracks be damaged and cut off. Threat to human life. Threat to animals. Measures to reduce the destructive effects of floods: Building and raising embankments on river banks and enlarging river channel enabiing it to e water ane oes coeliyel and channels to divert fioods from populated areas bioae cthills and planti f@ trees to check and weaken the flow i i station on fosthills and planting mor Discouraging deforesta saat ony ottl it reas within the reach of floods. and populations settlements in are: . Preventing bllngs per ae war system, warn people tou eecONE Improvin: and fi (radlo, Wi and print (newspapers) 10 i Improving reliof (iramediate avon’ pciai bodies, e.g. POMA (Pakistan bilitaticn (long term steps) service: anagemeni Autharity), by ereating \