Dr. SaMeH S. Ahmed

Civil and Environmental Engineering Department

Precipitation


Precipitation



In meteorologyprecipitation (also known as one of the classes of hydrometeors, which are atmospheric water phenomena) is any product of the condensation of atmospheric water vapor that falls under gravity.[1] The main forms of precipitation include drizzle (sometimes called mist - especially "Scotch mist"), rainsleetsnowgraupel andhail. Precipitation occurs when a local portion of the atmosphere becomes saturated with water vapour, so that the water condenses and "precipitates". Thus, fog and mist (except when the terms are used to mean "drizzle") are not precipitation but suspensions, because the water vapour does not condense sufficiently to precipitate. Likewise,frost does not precipitate out of the atmosphere but rises from the ground; so it, too, is not precipitation.[2] Two processes, possibly acting together, can lead to air becoming saturated: cooling the air or adding water vapour to the air. Generally, precipitation will fall to the surface; an exception is Virga which evaporates before reaching the surface. Precipitation forms as smaller droplets coalesce via collision with other rain drops or ice crystals within acloud. Rain drops range in size from oblate, pancake-like shapes for larger drops, to small spheres for smaller drops. Unlike raindrops, snowflakes grow in a variety of different shapes and patterns, determined by the temperature andhumidity characteristics of the air the snowflake moves through on its way to the ground. While snow and ice pellets require temperatures close to the ground to be near or below freezing, hail can occur during much warmer temperature regimes due to the process of its formation.

Moisture overriding associated with weather fronts is an overall major method of precipitation production. If enough moisture and upward motion is present, precipitation falls from convective clouds such as cumulonimbus and can organize into narrow rainbands. Where relatively warm water bodies are present, for example due to water evaporation from lakes,lake-effect snowfall becomes a concern downwind of the warm lakes within the cold cyclonic flow around the backside of extratropical cyclones. Lake-effect snowfall can be locally heavy. Thundersnow is possible within a cyclone's comma head and within lake effect precipitation bands. In mountainous areas, heavy precipitation is possible where upslope flow is maximized within windward sides of the terrain at elevation. On the leeward side of mountains, desert climates can exist due to the dry air caused by compressional heating. The movement of the monsoon trough, or intertropical convergence zone, brings rainy seasons to savannah climes.

Precipitation is a major component of the water cycle, and is responsible for depositing the fresh water on the planet. Approximately 505,000 cubic kilometres (121,000 cu mi) of water falls as precipitation each year; 398,000 cubic kilometres (95,000 cu mi) of it over the oceans and 107,000 cubic kilometres (26,000 cu mi) over land.[3] Given the Earth's surface area, that means the globally averaged annual precipitation is 990 millimetres (39 in), but over land it is only 715 millimetres (28.1 in). Climate classification systems such as the Köppen climate classification system use average annual rainfall to help differentiate between differing climate regimes. The urban heat island effect may lead to increased rainfall, both in amounts and intensity, downwind of cities. Global warming is also causing changes in the precipitation pattern globally. Precipitation may occur on other celestial bodies, e.g. when it gets cold, Mars has precipitation which most likely takes the form of ice needles, rather than rain or snow.

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For CE 370 students : Your second midterm exam will be on Wednesday 27 March 2019. In the surveying lab

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Mining Engineering


Mining engineering is an engineering discipline that involves practice, theory, science, technology, and the application of extracting and processing minerals from a naturally occurring environment. Mining engineering also includes processing minerals for additional value.

Environmental Engineering


Environmental engineers are the technical professionals who identify and design solutions for    environmental problems. Environmental engineers provide safe drinking water, treat and properly dispose of wastes, maintain air quality, control water pollution, and remediate sites contaminated due to spills or improper disposal of hazardous substances. They monitor the quality of the air, water, and land. And, they develop new and improved means to protect the environment.

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Assuit University (Home University), Egypt


Imperial College, London, UK


Faculty of Engineering, Al-Mergeb University, Libya


King Saud University, KSA

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Course 2018/19-2


  1. Surveying 1 CE 370
  2. Surveying II  CE 371
  3. Senior Design II  (round 6) CE 499




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Member of the Editorial Board: " Journal of Water Resources and Ocean Sciences"  2013 till now

https://www.researchgate.net/profile/Sameh_Ahmed5/?ev=hdr_xprf

Participating in The Third International Conference on Water, Energy and Environment,(ICWEE) 2019 - American University of Sharjah, UAE 26-28 March 2019 with a Paper and Poster

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2nd Midterm Exams on 3/4/2019

Student Conference



Participation  in the 6Th Student Conference

With a paper and oral presentation

From the Senior Design Project CE499 -35

See inside, the paper, and presentation

CE 370 Course

Surveying I

2018-2019S




Power point


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Lecture notes
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3-4-2019

:Second Midterm Exam



Results


Model Answer
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Working  marks is available -Click on Surveying I

CE 371 Course

Surveying II

2018-2019-2




Lectures





First midterm exam


Lab


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Working marks out of 60 is  available- Click on Surveying 2

CE 474 Course

Photogrammetry

2018-2019-1



Available 0-1-2-3-4 Power point

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Quizzes 2 and 3 with model Answer

Quizzes
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Student Performance Records


CE 499 Course

Senior Design 2


Second Best paper from Senior Design Projects in 2015

Paper title:

Evaluation of Groundwater Quality Parameters using Multivariate Statistics- a case Study of Majmaah, KSA

Students:

Abdullah A. Alzeer

Husam K. Almubark

Maijd M. Almotairi

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Civil and Environmental Engineering Department
College of Engineering, Majmaah University
Majmaah, P.O. 66, 11952, KSA

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