Clouds & Orographic Precipitation Practical

Overview

This page describes a practical exercise for the Virtual Tenerife Field Trip to aid in the understanding of the distribution of precipitation over the Island. Precipitation and the availability of water has a strong impact on Ecology over the island, as you will see throughout the week. The model used is a single column model (SCM), which models processes in a 1-dimensional column of air. At every level in the vertical the model calculates the evolution of cloud microphysical processes, such as:

condensation onto aerosol
collision-coalescence of drops
initiation of the ice phase
formation of precipitating particles (rain, snow)
and many more processes

It also calculates the transport of precipitation between vertical levels, which is a dominant transport mechanism here.

This column of air is lifted over a mountain and cools, allowing more condensation to take place. The extra condensation can be enough to initiate precipitation, which then falls to Earth. The model can be used to illustrate the following phenomena:

The effect of variations in cloud drop number concentrations on precipitation
The effect of varying temperatures on idealised clouds and precipitation
The effect of cloud depth on precipitation.
The distribution of precipitation in idealised clouds

Instructions

Go to this web-page (password protected / link opens in new tab). You may want to arrange your browser windows so that you have this page and the tab that opens visible at the same time.

Running the model

Running the model is straightforward, press the "Run Model" button and wait for around 30 seconds. The model will run on a computer at the University of Manchester and then this computer will open the output file and make 4 plots, which are then displayed on the web page.

The idea for the practical is that you will run the model for different scenarios. Once the simulation completes you should right click on the image to download it, save it to your computer and make notes for later.

Examples

(a) shows the cloud droplet number concentration (CDNC); (b) shows the liquid water mixing ratio, \(q_c\); (c) shows the rain water mixing ratio, \(q_r\); (d) shows the ice crystal number concentration, \(N_{ice}\). The red patch shows the location of the mountain over which the air is lifted. Height of the mountain is around 1 km, similar to the Anaga.

clouds_notes.pdf