Lapse Rates

[Jon Miller]

What's a good web site for forecast Lapse Rates ?
Thanks for any info.

Jon Miller
KT8NDO

 

[Chris Nuttall]

I'm not sure of any off-hand that show the exact numbers for the lapse rates but all you have to do is look at forecast soundings to see forecast lapse rates.

 

[Karla Dorman]

What ARE lapse rates, anyway? How is it related to severe storm formation? Thanks for any help in advance ...

 

[mikegeukes]

Earl Barker 0-2km, 0-3km Lapse Rates:
http://www.wxcaster.com/smallfiles_central_svr.htm

Earl Barker: 850-500mb Lapse Rates:
http://128.121.193.153/central_models.htm
http://www.wxcaster.com/conus_0012_us_models.htm

NCEP 850-500mb Lapse Rates:
http://www.emc.ncep.noaa.gov/mmb/namsvrfcst/
http://www.emc.ncep.noaa.gov/mmb/rucsvrfcst/

 

[Bill Schintler]

What ARE lapse rates, anyway? How is it related to severe storm formation? Thanks for any help in advance ...

The temperature of the atmosphere decreases with height because of lower air density... Lapse rates simply quantify the decrease of temperature over a height range. The most common standard lapse rates are "low-level" (fall in temperature, degrees C, from surface through 3 Km above the surface - about a 9,000 ft range), and "mid-level" - usually 700mb to 500mb - or 10,000ft through 18,000 ft. When I'm doing a forecast, I usually compare the temperatures on the 700mb and 500mb forecast charts to determine the mid-level forecast lapse rates. I also look at 00Z soundings for the day preceding forecast period, and note mid-level lapse rates on upstream soundings - soundings of the mid-level environment that will be advected into the forecast area of interest 18-24 hours later. Often we see "differential advection" of steep mid-level lapse rates from the southwest states along with moisture from the Gulf - usually from the surface through about 5000 ft... This can set the stage for an unstable environment...

Why are lapse rates important? the steeper the lapse rates are (especially mid-level), the greater potential for instability (CAPE) - given sufficient moisture in the low-levels of the atmosphere (which is lacking today and tomorrow).

- bill

 

[Jason Boggs]

What ARE lapse rates, anyway? How is it related to severe storm formation? Thanks for any help in advance ...

I suggest these readings in order to learn about lapse rates...

LAPSE RATES

Also, just google lapse rates and you can find all kinds of info to learn about.

 

[Matthew K. Hartman]

I wrote up a tutorial on lapse rates several years ago, at a friend's request, if it would help. It's a little lengthy, but I try to include how to calculate them manually and how to visualize them on a sounding:

http://www.mhartman-wx.com/fcst_tools/lapse_rates.html

 

[Steve Miller TX]

What ARE lapse rates, anyway? How is it related to severe storm formation? Thanks for any help in advance ...

As far as what lapse rates are, I'll give a simple explanation using a math calculation. You will need to determine 4 variables:

T1 = temperature in celsius at a particular level in the atmosphere.

T2 = temperature in celsius at a higher level in the atmosphere.

H1 = height in meters of T1

H2 = height in meters of T2

So, with that info at hand, you can calculate a lapse rate for any range in the atmosphere.

((T1 - T2) / (H2 - H1)) * 1000 = lapse rate per 1000 meters

When using millibar heights in the atmosphere to convert to meters:

1000 mb-- near surface
850 mb-- 1,500 meters (5,000 feet)
700 mb-- 3,100 meters (10,000 feet)
500 mb-- 5,500 meters (18,000 feet)
300 mb-- 9,300 meters (30,000 feet)


If you have 20C at 850mb(1500 meters) and -15C at 500mb(5500 meters):

((20 - -15) / (5500 - 1500)) * 1000

is....

(35 / 4000) * 1000

is......

.00875 * 1000

which gives you a lapse rate of......

8.75 C/km

which is another way of saying....

The temperature decresease at a rate of 8.75 degrees celsius for every 1000 meters.

 

[Steve Dedman]

I wrote up a tutorial on lapse rates several years ago, at a friend's request, if it would help. It's a little lengthy, but I try to include how to calculate them manually and how to visualize them on a sounding:

http://www.mhartman-wx.com/fcst_tools/lapse_rates.html

Great tutorial!!!

I have a question tho...

So, I'm subtracting 65 meters from 1595 meters to get my layer thickness.

What specific layer are you referring to? PBL? Dry adiabatic lapse layer? Why do you subtract it out?