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lookingnorth

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    Central/Western Medium-Long Range Discussion

    in Central/Western States

    Posted

    On 8/27/2021 at 11:56 AM, Powerball said:

     

    How many other years, besidea 2004, has OKC not hit 100*F+?

    DFW has only had 6 so far, and they all occured in that late July / early August period.

    I now know better than to say it won't happen for sure, especially with the help of subsidence behind Ida next week, but it is getting increasingly less likely that DFW will see any more 100*F+ days this year.

    19 other years

    • Like 1

    Historic Pacific Northwest Heatwave of 2021

    in Climate Change

    Posted

    1 hour ago, donsutherland1 said: 
    
000
NOUS46 KOTX 300126
PNSOTX
IDZ001>004-026-027-WAZ031>038-041>044-301326-

Public Information Statement
National Weather Service Spokane WA
626 PM PDT Tue Jun 29 2021

...PRELIMINARY HIGH TEMPERATURE REPORTS...

Location                     Temp      Time/Date       Provider

...Idaho...
...Chelan County...
3.6 SE Ardenvoir             119 F     0130 PM 06/29   HADS
1.2 S Peshastin              119 F     0345 PM 06/29   HADS

     

    If those 119's are verified, that would be a state record for Idaho, right?

    • Like 1

    Historic Pacific Northwest Heatwave of 2021

    in Climate Change

    Posted

    18 hours ago, donsutherland1 said: 
    
Weather summary
for British Columbia
issued by Environment Canada
at 5:36 p.m. PDT Monday 28 June 2021.

Discussion.

The following data is preliminary and will be updated later tonight 

The following areas will have set a daily maximum temperature record 
on June 28, 2021: 

Abbotsford Area (Abbotsford A) 
Preliminary new record of 42.9 
Old record of 32.4 set in 2008 
Records in this area have been kept since 1944 

Dawson Creek Area (Dawson Creek A) 
Preliminary new record of 38.1 
Old record of 27.8 set in 2015 
Records in this area have been kept since 1926 

Gibsons Area (Sechelt Aut) 
Preliminary new record of 40.1 
Old record of 29.6 set in 2008 
Records in this area have been kept since 1949

     

    Looks like some places broke their daily records by over 10°C!

    • Like 1

    Adiabatic lapse rate

    in Climate Change

    Posted

    On 12/13/2020 at 10:46 AM, Leitwolf said:

    The adiabatic lapse rate is the key component of the GHE. Regrettably I do not seem to fully understand it and so I need to ask for help.

    The average lapse rate on Earth is about 6.5K/1km. The "dry" lapse rate however is said to be 9.8K/km. So vapor (and the latent heat it transports) reduces the lapse rate significantly, in this way it also serves as a kind of anti-GHG. I mean if we understand the GHE as a combination of an elevated emission layer (photosphere) where we have 255K and the adiabatic lapse rate, which produces higher temperatures at the surface. Anyhow, the exact impact of vapor on the lapse rate is a key question.

    Now I found this sightly confusion chart on the subject on wikipedia. There are some things I understand, and some things I don't. For instance we have lines for altitude (scale on the right) which are sloped. That is to be understood relative to the left scale of pressure, meaning with cold air pressure will decrease faster with altitude, as it has a higher density.

    https://en.wikipedia.org/wiki/Lapse_rate#/media/File:Emagram.GIF

    Now if I look at the bold line for the dry adiabat, for instance the one starting at 20°C, it intersects the 5km line at roughly -24°C. That are 44K for 5km, or 10.8K/km, significantly more than the 9.8K quoted before. Assuming the chart is right, what causes this difference? Is it because the troposphere is naturally unstable and heated at the surface, so to say?

    Then the "wet" lapse rate starting at +15°C intersects the 5km line at about -14.5°C, meaning a delta of 29.5K or 5.9K/km. +15°C roughly corresponds to the actual surface temperatures on Earth, yet 5.9K/km is significantly less than the quoted 6.5K. Why is that? Is it representing a more theoretical perfectly wet atmosphere with a 100% H2O saturation??

    I have no idea why the dry adiabatic lapse rate is so great in the chart. I've only ever used Skew-T log-P charts, not emagrams. However, the moist adiabatic lapse rate varies significantly based on temperature, and 5.9K/km is well within the range of possibility. The average environmental lapse rate is not the same as the average moist lapse rate because sometimes the atmosphere will be dry adiabatic, sometimes there will be an inversion, etc. But since the atmosphere is often moist adiabatic, the two happen to be similar.

    Arctic Sea Ice Extent, Area, and Volume

    in Climate Change

    Posted

    On 11/1/2020 at 12:56 PM, bdgwx said:

    It's complicated. First understand that this is not entirely unexpected. In fact, the IPCC AR5 WG1 prediction for SH sea ice, although significantly more uncertain than predictions for the NH, shows a slight preference for increases through about 2030 with the possibility of record highs persisting even through 2060 before things turn south (pun intended) down there too. I must caveat that by saying the uncertainty envelope does include the possibility of the secular decline starting around 2020 as well. The unfortunate state of affairs with SH sea ice is that our understanding of its behavior in a warming world is still quite nebulous compared to our understanding of NH sea ice behavior. Second understand that the see-sawing of temperatures and sea ice between hemisphere has been shown to occur during previous significant climatic change events so it is not unprecedented nor is it inconsistent with climatic shifts.

    Anyway here are some things to consider...

    • The NH is characterized by ocean surrounded by land whereas the SH is land surrounded by ocean. This trivial fact accounts for the bulk of the differences between NH and SH sea ice behavior. The consequences of this can be quite dramatic and contradictory between the NH vs. SH.
    • A positive phase of the Southern Annular Mode (SAM) is associated with increasing SH sea ice. Global warming tips the SAM toward a positive phase.
    • ENSO negative/positive phases reinforce positive/negative SAM phases.
    • The Montreal Protocol through its ban of CFCs, repair of stratospheric ozone, associated cooling tendencies and other effects on weather patterns has been linked to SH sea ice increases.
    • Increasing GHGs actually have a cooling effect on the Antarctica continent itself especially during the SH winter when the upper atmosphere is often warmer than the surface. Remember, GHGs act like a thermal barrier preventing IR radiation from passing through. This causes the warm/cool side of the barrier to warm/cool further. Positive/negative lapse rates get more positive/negative. Antarctica often has a negative lapse rate during the winter so GHGs cause cooling at the surface and warming in the upper atmosphere. This effect (among others) suppresses polar amplification in the SH.

    Disclaimer...I'm not well informed regarding SH sea ice so hopefully others who know more about the behavior down there can chime in on points I've missed or mischaracterized.

    The main take away here is that sea ice is mainly a NH issue right now. Most scientists do not expect NH-style declines in sea ice down in the SH anytime soon. And the fact that the SH responds differently than the NH is probably more the rule than the exception. 

    I'm not an expert either, but I did a class project on it last spring and that's basically what I found. The change in lapse rates thing is new to me, but it makes total sense.

    Banter Thread

    in Southeastern States

    Posted

    On 5/5/2020 at 12:21 AM, Anonmet_GSO said:

    Not sure the best forum to post these questions/thoughts so here I am, and here goes.

    Posting this on May 5th after an exhaustive search for April NC average temperature departure from normal and I'm looking in the wrong places or it's not published.

    Here's where you can find the April NC average temperature departure. For some reason the mapping feature isn't working, but the table is still there.

    https://www.ncdc.noaa.gov/cag/statewide/mapping/110/tavg/202004/1/value

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