Page 5 of 5 < 1 2 3 4 5
Topic Options
#1457142 - 14/03/2018 13:01 Re: Atmospheric Rivers [Re: Flowin]
Locke Offline
Weatherzone Addict

Registered: 27/12/2007
Posts: 4440
Loc: Brisbane
What the hell just happened with the tdepth animation at CPC.

Must be a glitch.

_________________________
This post and any other post by Locke is NOT an official forecast & should not be used as such. It's just my opinion & may or may not be backed by sound meteorological data. For official information, refer to Australian Bureau of Meteorology products.

Top
#1457148 - 14/03/2018 14:04 Re: Atmospheric Rivers [Re: Flowin]
Locke Offline
Weatherzone Addict

Registered: 27/12/2007
Posts: 4440
Loc: Brisbane
Ooops posted in the wrong area. Meant to post this in the climate driver discussion.
_________________________
This post and any other post by Locke is NOT an official forecast & should not be used as such. It's just my opinion & may or may not be backed by sound meteorological data. For official information, refer to Australian Bureau of Meteorology products.

Top
#1457457 - 16/03/2018 22:09 Re: Atmospheric Rivers [Re: Flowin]
Seira Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7394
Loc: Adelaide Hills.
Originally Posted By: Flowin
Thanks for your post Seira. Interesting.
I understand difference between integrated water vapour transport and concentrated water stream. Eg a slow moving wide stream with good height giving large sectional area could produce high total water movement (volume/time). Whereas a concentrated stream is high water content on a particular path.

I will acknowledge language or grammatical errors/typos, but I'm finding it difficult interpreting the above.

There is potentially rather a lot of messy theoretical stuff/or novel ideas in this dialogue which may also need clarification.
_________________________
Silence can be beautiful because it is an avenue to peace of mind. Knowing oneself requires autonomy, an ability to laugh, and an acknowledgement one does not have all the answers...

Top
#1457459 - 16/03/2018 22:34 Re: Atmospheric Rivers [Re: Flowin]
Flowin Offline
Weather Freak

Registered: 15/10/2017
Posts: 402
Loc: Pinjarra Hills, Qld
Ok Seira. Take#2
I was attempting to describe the difference between flux and concentration.
I guess I did not explain it well🙃

Top
#1457818 - 18/03/2018 20:35 Re: Atmospheric Rivers [Re: Flowin]
Seira Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7394
Loc: Adelaide Hills.
Originally Posted By: Flowin
Ok Seira. Take#2
I was attempting to describe the difference between flux and concentration.
I guess I did not explain it well🙃


Ok smile .

My understanding is flux is usually from one region (in space and time) to another, involving a reason to transport energy from one to the other. Concentration would be density (units of some substance per a given volume).

I see no issue with using Atmospheric Rivers as a descriptive idea smile ...however beyond that (into theoretical realms) it can become tedious/messy. My impression anyway.


Edited by Seira (18/03/2018 20:42)
_________________________
Silence can be beautiful because it is an avenue to peace of mind. Knowing oneself requires autonomy, an ability to laugh, and an acknowledgement one does not have all the answers...

Top
#1458264 - 21/03/2018 14:03 Re: Atmospheric Rivers [Re: Seira]
Flowin Offline
Weather Freak

Registered: 15/10/2017
Posts: 402
Loc: Pinjarra Hills, Qld
regarding your comment Seira "I see no issue with using Atmospheric Rivers as a descriptive idea smile "

I agree if you're seeking a clear definition. Similar to East Coast Lows many people want to label any low off the east coast as an ECL, but I understand that BoM do have some criteria for ECLs.

Back to ARs. The American Meteorological Society have put some definition on AR extents "Average width is based on atmospheric river boundaries defined by vertically integrated water vapor transport (IVT; from surface to 300 hPa) lateral boundary threshold of 250 kg m−1 s−1. Depth corresponds to the altitude below which 75% of IVT occurs. The total water vapor transport (a.k.a. flux) corresponds to the transport along an atmospheric river, bounded laterally by the positions of IVT = 250 kg m−1 s−1 and vertically by the surface and 300 hPa.".
Link: http://glossary.ametsoc.org/wiki/Atmospheric_river
_________________________
Models are for estimating and gauges are for knowledge.

Top
#1458617 - 23/03/2018 21:09 Re: Atmospheric Rivers [Re: Flowin]
Seira Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7394
Loc: Adelaide Hills.
Originally Posted By: Flowin
The American Meteorological Society have put some definition on AR extents "Average width is based on atmospheric river boundaries defined by vertically integrated water vapor transport (IVT; from surface to 300 hPa) lateral boundary threshold of 250 kg m−1 s−1. Depth corresponds to the altitude below which 75% of IVT occurs. The total water vapor transport (a.k.a. flux) corresponds to the transport along an atmospheric river, bounded laterally by the positions of IVT = 250 kg m−1 s−1 and vertically by the surface and 300 hPa.".
Link: http://glossary.ametsoc.org/wiki/Atmospheric_river

Hi Flowin smile ,

Do you understand the glossary's description? Also, bear in mind itís for the northern hemisphere.
_________________________
Silence can be beautiful because it is an avenue to peace of mind. Knowing oneself requires autonomy, an ability to laugh, and an acknowledgement one does not have all the answers...

Top
#1458708 - 24/03/2018 12:34 Re: Atmospheric Rivers [Re: Flowin]
Seira Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7394
Loc: Adelaide Hills.
Originally Posted By: Flowin
regarding your comment Seira "I see no issue with using Atmospheric Rivers as a descriptive idea smile "

I agree if you're seeking a clear definition. Similar to East Coast Lows many people want to label any low off the east coast as an ECL, but I understand that BoM do have some criteria for ECLs.

My understanding is that without clear definitions, there is no science!


Edited by Seira (24/03/2018 12:38)
_________________________
Silence can be beautiful because it is an avenue to peace of mind. Knowing oneself requires autonomy, an ability to laugh, and an acknowledgement one does not have all the answers...

Top
#1459299 - 27/03/2018 00:53 Re: Atmospheric Rivers [Re: Flowin]
Flowin Offline
Weather Freak

Registered: 15/10/2017
Posts: 402
Loc: Pinjarra Hills, Qld
Seira, agree science needs clear definitions. And along the way to getting to those clear definitions some vague and evolving definitions from early work of scientists with an idea informed with observational experience of "weather" makes it all the more interesting smile

Regarding my understanding of the "North American" AMS glossary it is something like,
A width and depth is needed to define spatial "extent" (cross section of the "weather system")
Width is defined by contours of the product of concentration kg/m3 and speed m/s. Something similar to flux per unit width and unit depth of a cross section.
Depth is defined by height that is below approx 75% of total depth-integrated precipitable water vapour up to 300 hPa
If my understanding is incorrect then I am happy to be corrected.:)👍


Edited by Flowin (27/03/2018 00:58)
_________________________
Models are for estimating and gauges are for knowledge.

Top
#1459597 - 28/03/2018 19:33 Re: Atmospheric Rivers [Re: Flowin]
Seira Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7394
Loc: Adelaide Hills.
Originally Posted By: Flowin
Seira, agree science needs clear definitions. And along the way to getting to those clear definitions some vague and evolving definitions from early work of scientists with an idea informed with observational experience of "weather" makes it all the more interesting smile

Regarding my understanding of the "North American" AMS glossary it is something like,
A width and depth is needed to define spatial "extent" (cross section of the "weather system")
Width is defined by contours of the product of concentration kg/m3 and speed m/s. Something similar to flux per unit width and unit depth of a cross section.
Depth is defined by height that is below approx 75% of total depth-integrated precipitable water vapour up to 300 hPa
If my understanding is incorrect then I am happy to be corrected.:)👍

I have little issue with what you have conveyed as your understanding....however that is not the reason I asked. The point I have been trying to get at is, as far as I can tell, water vapour does not have a depth in the atmosphere -- it has a concentration, which can be measured in kilograms per unit volume (e.g. cubic metre)....precipitable water is a theoretically derived equation, which is not the same as integrated water-vapour transport [IWVT],....and I find it difficult reconciling IWVT with the idea of integration itself.

My understanding is integration requires:
=> A equation that can be integrated (with some variable).
=> Taking the integral of that equation (over a definite range, e.g. X=1 to X=0).
=> Plugging figures into the integrated equation (variable X) over that definite range to get an outcome.

That is my insight smile .


Edited by Seira (28/03/2018 19:43)
_________________________
Silence can be beautiful because it is an avenue to peace of mind. Knowing oneself requires autonomy, an ability to laugh, and an acknowledgement one does not have all the answers...

Top
#1459641 - 29/03/2018 08:55 Re: Atmospheric Rivers [Re: Flowin]
Flowin Offline
Weather Freak

Registered: 15/10/2017
Posts: 402
Loc: Pinjarra Hills, Qld
Seira, thanks. I think I now understand the point you were raising smile , and yes water vapour does not have a depth in the atmosphere.

I agree an equation that can be integrated with respect to a variable and over a defined range is needed for mathematical completeness.
I simply think of integration when in relation to matters such as concentration or water flow as "aggregate", "total", or "sum".
E.g. concentration in kg/m3 multiplied by a defined volume m3 yields kg. Similarly flow in m3/s multiplied by a defined time period yields m3. In that way of describing it you can replace words "multiplied by" with "integrated over".

Water vapour as a concentration kg/m3 integrated with the depth of the atmosphere (assuming some upper level can be defined above which there is minimal water vapour) yields kg/m2 which I understand to be total precipitable water. It appears commonly expressed as depth in mm assuming density of water as 1000 kg/m3 (but more strictly TPW should be said as units of kg/m2).

If that "total depth" of precipitable water is moving (assuming laterally), it is a transport of TPW in kg/m2 multiplied by speed in m/s which yields kg/m/s (or kg m-1 s-1).

So yes TPW is not the same as IWVT as TPW does not have the movement component, whereas IWVT does have the movement component.

I hope that makes sense, does not contain errors, and is relevant to your point.

Top
#1459776 - 30/03/2018 13:55 Re: Atmospheric Rivers [Re: Flowin]
Seira Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7394
Loc: Adelaide Hills.
I can understand where you're going, smile .... perhaps this will help as well:

Depending on where you are....water-vapour makes up between 1 and 4% of the mass of air by volume, at sea-level. In that sense you are accurate in saying, more-or-less, there would have to be a cut-off minimum concentration at which this gas determines the total integration [with altitude] of IWV. However, because water-vapour can be so variable in the troposphere, it is difficult, unless direct measurements are made, to say whether there will be just one cut-off in the vertical [and horizontal], or more than one. If there is more than one, the integral would become fragmented and incomplete....without such measurements [in space and time] this, realistically, cannot be ruled out.

So, in a nutshell, IWVT has to take into account variations in the integral with space and time, which, I'd think, would make it far more complex.

The other thing one would have to be careful about is calling every little "feature" on a weather map an Atmospheric River, because its water-vapour concentration exceeds -- however confined or narrow -- that of the minimum cut-off.


Edited by Seira (30/03/2018 13:59)
_________________________
Silence can be beautiful because it is an avenue to peace of mind. Knowing oneself requires autonomy, an ability to laugh, and an acknowledgement one does not have all the answers...

Top
#1460575 - 03/04/2018 07:51 Re: Atmospheric Rivers [Re: Seira]
Flowin Offline
Weather Freak

Registered: 15/10/2017
Posts: 402
Loc: Pinjarra Hills, Qld
I agree the vertical integration of water vapour is not straight forward, nonetheless some attempt to estimate total precipitable water helps to get a feel for water in the atmosphere, better than say water vapour loop from Satellite image.

Originally Posted By: Seira

The other thing one would have to be careful about is calling every little "feature" on a weather map an Atmospheric River, because its water-vapour concentration exceeds -- however confined or narrow -- that of the minimum cut-off.


I agree also an AR is not just any feature showing "higher" water vapour concentration.
I think the American Meteorological Society definition part way helps to clarify some definition for an Atmospheric River - which I might simplify to "sufficient total depth of water content in the atmosphere, combined with movement, and spatial extent such that the feature can transport a lot of water"


Edited by Flowin (03/04/2018 07:52)

Top
#1460761 - 03/04/2018 19:58 Re: Atmospheric Rivers [Re: Flowin]
Seira Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7394
Loc: Adelaide Hills.
I find your resilience with regard to this discussion quite admirable Flowin smile . Despite discrepancies there might be in our perspectives smile .
_________________________
Silence can be beautiful because it is an avenue to peace of mind. Knowing oneself requires autonomy, an ability to laugh, and an acknowledgement one does not have all the answers...

Top
#1460767 - 03/04/2018 20:12 Re: Atmospheric Rivers [Re: Seira]
Flowin Offline
Weather Freak

Registered: 15/10/2017
Posts: 402
Loc: Pinjarra Hills, Qld
Originally Posted By: Seira
I find your resilience with regard to this discussion quite admirable Flowin smile . Despite discrepancies there might be in our perspectives smile .

Fair comment Seira. Going back to where I started from
Originally Posted By: Flowin

Has anybody heard of "atmospheric rivers" in the Australian context?

Definition of the feature, or say AR event criteria clarification is important.
I have appreciated your questioning, and have learnt along the way😀

Top
#1461481 - 11/04/2018 20:16 Re: Atmospheric Rivers [Re: Flowin]
Seira Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7394
Loc: Adelaide Hills.
Originally Posted By: Flowin
I have appreciated your questioning, and have learnt along the way😀

And it's reciprocated smile !
_________________________
Silence can be beautiful because it is an avenue to peace of mind. Knowing oneself requires autonomy, an ability to laugh, and an acknowledgement one does not have all the answers...

Top
#1461696 - 13/04/2018 21:23 Re: Atmospheric Rivers [Re: Flowin]
Flowin Offline
Weather Freak

Registered: 15/10/2017
Posts: 402
Loc: Pinjarra Hills, Qld
Another observation I have from literature on ARs in research effort from California seems to me to identify more occurrences of ARs in winter.
I am yet to explore whether that means anything for AR like weather events for Australia.

Top
#1461721 - 14/04/2018 10:09 Re: Atmospheric Rivers [Re: Flowin]
retired weather man Offline
Weatherzone Addict

Registered: 01/07/2007
Posts: 4485
Loc: Wynnum
My guess is our version would be Autumn to late Winter NW cloud bands, many of which used to spawn ECL's and don't seem to be as frequent these days.
_________________________
Wyn Nth 2018-Jan12.2(158),Feb264.4(146),Mar217.0(126),Apr65.8(96)YTD558.4(527.3),

Top
#1462062 - 19/04/2018 06:30 Re: Atmospheric Rivers [Re: Flowin]
wilyms Offline
Weather Freak

Registered: 06/03/2013
Posts: 145
Loc: Roma, Qld
News.com just published something useful and relevant to this thread!

http://www.news.com.au/technology/enviro...e33525623c9302f

Top
Page 5 of 5 < 1 2 3 4 5


Who's Online
4 registered (ashestoashes, Stormy3, 2 invisible), 352 Guests and 3 Spiders online.
Key: Admin, Global Mod, Mod
Today's Birthdays
araT, danz, kimsmith, Tara, Welshmun
Forum Stats
29544 Members
32 Forums
23883 Topics
1489499 Posts

Max Online: 2925 @ 02/02/2011 22:23
Satellite Image