Sign In | Sign Up | Help | Invite    
Advanced Search Ask A Question Community Recent Changes
My:             Contributions   
Contributors
{for ul in pageInfo.page}
${ul.nickName}
{var al = toBreakWord(ul.adUrl,18)} {if ul.adSentence !=''}${ul.adSentence}
{/if} {if ul.adUrl !=''}${al}
{/if}
 
{/for}
Earn Free Advertising   +   Earn Money By Writing What You Know at WISTEME.COM
Question Discussion History

Edit
    Question ID:   19750         Current Version: 1
Question: Why is the air warmer near the earth's surface?
Category: Science > Weather
Keywords: air, atmosphere, warmer, earth, surface, temperature
Type: why
Rating:(0 ratings)    Views: 13    Discussions: 0   In Watch Lists: 1  

 
    Answer:

The general rule of thumb used by meteorologists is that temperature decreases approximately 3.6 degrees F per 1000 feet in the troposphere (the lowest layer of the atmosphere, where we live). This is an average value and varies from season to season. The decrease is slightly less in the summer and slightly greater in the winter.

The atmosphere receives about one-eighth of its heat directly from the Sun in the form of short-wave radiation absorption, but receives almost 70 percent, or 6 times as much heat from the earth, in the form of long-wave radiation.

Earth's surface is primarily from long wave radiation. The very lowest part of the atmosphere, called the boundary layer (up to about 1.5 kilometers on a normal day) warms from the warmer earth surface (mostly by long wave radiation), with the warmer air being mixed upwards by convective air parcels (air warmer than the surrounding air) and mechanical turbulence (from wind). As the air rises (and expands, thereby decreasing in air pressure) it cools, resulting in the adiabatic lapse rate. Since temperature and pressure are roughly proportional for the same volume of air, the temperature decreases with height (during the day).

Long wave radiation is absorbed by the air, primarily water vapor, carbon dioxide, and methane in the air (so-called "greenhouse gases"). Since there is a greater concentration of these gases near the earth's surface, more is absorbed closest to the surface and less with increasing height. Therefore, for this reason also, during the day, the temperature decreases with height in the boundary layer.

So, adiabatic cooling and the distance from the earth's surface are both important. Long wave radiation is most effective in heating the air, with direct contact of the air with the ground being less important.

At night, long wave radiation continues to be lost from the Earth's surface (a lot during cloudless nights) and often causes the temperature at the surface to become less than at greater heights, causing a slight increase in temperature with height (called an inversion) and a decrease in the height of the boundary layer to as little as 300 meters.

Sources:

[1] Dale Bechtold, David Cook, "Heating in the Atmosphere", Online posting. NEWTON BBS Ask a Scientist.

[2] David Cook, "Temperature and Atmosphere", Online posting. NEWTON BBS Ask a Scientist.

Read more questions from WISTEME through
     Add to MSN Add to My AOL
 Rate this Question
   Add to Groups   Add to Watch Lists   Share Question
                          
     Question ID:  ${question.id}         Current Version:  ${question.version}

{for qh in questionHistory} {if qh.status == 'r'} {else} {/if} {/for}
Version Contributor Date (ET) Voting
${qh.version} ${qh.nickName} ${qh.date} Rejected
${qh.version} ${qh.nickName} ${qh.date} {if qh.status != 'c'} {if qh.status == 'a'} Approved {else} {if qh.rstatus == 'c'} On-going {else} Pending {/if} {/if} {else}   {/if}
Start a New Topic
ID Topics Replies Latest Post (ET)
{if dlist!=null} {for d in dlist} {/for}
${parseInt(d_index)+1} ${d.sentence} ${d.replyNum} ${d.lastestDate}
{else}
No discussion topic.
{/if}
Label Name:
 
Group Name:
 
 
{else}
     You have no group.
{/if}
Advertisements
{if advertisements.length > 0} {else} {/if}
{for ad in advertisements}
${ad.adTitle}
${ad.adSentence}
${ad.adUrl}
{/for}

Home | About Us | Terms of Use | Privacy Policy | Browse Questions | RSS Feed

Copyright ©2010 WISTEME LLC. All Rights Reserved.