Factors Affecting Temperature: Wind and Mixing

Introduction

In the prerequisite module "Radiation and the Diurnal Heating Cycle", we learned a fundamental aspect about how the temperature changes in the atmosphere: it's almost entirely driven by the radiation absorbed and emitted by the Earth's surface. The atmosphere absorbs and emits comparatively little, enough to only affect the air temperature directly by a couple of degrees Celsius.

In forecasting the temperature on a daily basis, there are three major considerations: How much radiation will reach the Earth, how much will be absorbed by the Earth and cause it to warm, and how will that warming be distributed in the atmosphere? This module focuses on factors governing the distribution of heating or cooling from the ground into the atmosphere. This involves two important processes: wind and mixing.

Learning Objectives

• To understand the difference between mechanical and thermally driven turbulence and their roles in affecting surface air temperatures.
• To understand how and why winds affect the nighttime temperature (and not the daytime temperature).
• To be able to forecast the effect of winds on daily high and low temperatures.

Table of Contents

1. Quick Quiz: How Does Heat Move?
2. Conduction
3. Convection
4. How the Atmosphere Gets Heated and Cooled
5. The 850 mb Forecasting Technique
6. The Daytime Boundary Layer
7. The Nighttime Boundary Layer
8. Summary

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