Tropopause information

C-Nimbus · Unread post by **C-Nimbus** » Wed 25/02/2004 08:41

Where can I find information regarding the daily height fluctuations of the Tropopause.

I notice that NZStorm always has information on the height, and I would like to know where this info can be found.

Any help??

C

GraemeWi · Unread post by **GraemeWi** » Wed 25/02/2004 12:16

They are in the soundings - they return the pressure where the tropopause was encountered and by extrapolation you can work out the altitude. The soundings return the height of each sounding level so that gives a base to use for extrapolation.

A sounding looks like this:
TTAA 7111/ 93112
99013 14611 19004 138 15629 85500 7840 70077 1150 50568 17364
40731 28391 30931 439// 25051 523// 20193 559// 15376 545// 10630
617// 88226 565// 88119 621//=|

The height of the tropopause is in the 4th to last block and the last three digits of that block is the mb level where the tropopause was encountered. If there is not 88 to the left of those digits, there no tropopause was recorded.

G

Michael · Unread post by **Michael** » Wed 25/02/2004 12:31

Who cares

We just want to know when are we going to get a decent day without wind or rain

C-Nimbus · Unread post by **C-Nimbus** » Wed 25/02/2004 15:25

LOL at Michael!!!

Thanks for the info GraemeWi.

Just one more question, do you have a link for these soundings?

Gary Roberts · Unread post by **Gary Roberts** » Wed 25/02/2004 17:13

Michael wrote:Who cares We just want to know when are we going to get a decent day without wind or rain

wxgirl · Unread post by **wxgirl** » Wed 25/02/2004 17:18

You just have a file with all these brilliant blue sky pictures to pull out to taunt us with don't you Gary? Least we won't be shivering out butts off as quite much as you tonight!

Gary Roberts · Unread post by **Gary Roberts** » Wed 25/02/2004 17:45

wxgirl wrote:Least we won't be shivering out butts off as quite much as you tonight!

'Tis a labor of love...plus it's a scary drive down again...

GraemeWi · Unread post by **GraemeWi** » Wed 25/02/2004 17:45

The NZ soundings can be found at http://www.metservice.co.nz/observation ... r_data.asp

The part I use is 'Part A'. There is a very cryptic explanation at http://www.metservice.co.nz/observation ... _codes.asp

There is a far better explanation on how to extract data at http://www.ems.psu.edu/Courses/Meteo200 ... t_ttaa.htm

I used this to build an Excel spreadsheet that takes a sounding and extracts the data. Other people use Skew-T charts which are generated from the soundings and contain some other difficult to calculate data like the LI. (There is no shortage of people who know how the LI is calculated, but very few that can explain how to actually do it)

This is a good Skew-T source: http://bomw0007:[email protected] ... /IDS65024/

or http://weather.admin.niu.edu/machine/sound.html (use station 93112 for Whenuapai)

Cheers,

Graeme

NZstorm · Unread post by **NZstorm** » Wed 25/02/2004 17:58

For upper air info I go straight to a skew-t Chart.

Todays midday sounding.

http://weather.admin.niu.edu/machine/sound.html

NZstorm · Unread post by **NZstorm** » Wed 25/02/2004 18:16

On the skew-t, the temperature is the right hand line. The dewpoint is to the left. The yellow line in the middle is the saturated adiabatic lapse rate (which is not relevant for the purpose of this discussion)

The tropopause is often easily spotted on the skew-t as where temperature starts warming near the top of the sounding. On todays sounding the trop is at 195hpa. On the left hand side of the skew-t, the heights in metres ae given. The trop looks to be about 12200m.
Remember that heights in meteorology are normal expressed in pressure.(hpa).

One other point, if you use the storm machine for skew-t you will need to know the following 4 digit identifier number. NZWP for Auckland.
There are two soundings a day. 00Z, 12Z.

NZstorm · Unread post by **NZstorm** » Wed 25/02/2004 18:21

Graeme, I have only just noticed your last post. We are covering the same ground essentially.

On those BOM soundings, both the SALR and the stability indices are forecast. Hence, don't take to much notice of the LI given. Its normaly inaccurate.