tag:blogger.com,1999:blog-2313427464944392482.post6121947400390738062..comments2024-03-25T05:30:23.847+11:00Comments on HotWhopper: Looking at Clouds with Ulrike Lohmann at AGU14Souhttp://www.blogger.com/profile/08818999735123752034noreply@blogger.comBlogger9125tag:blogger.com,1999:blog-2313427464944392482.post-13726041270235692682014-12-19T07:35:39.343+11:002014-12-19T07:35:39.343+11:00Ulrike Lohman is one of my research heroes from th...Ulrike Lohman is one of my research heroes from the time I was working on cloud structure. She has such an enormous wide range of knowledge, from cloud microphysics (all the different cloud particles and how they form) to cloud dynamics, climate modelling and the assessment of the influence of clouds on climate (radiative forcing). Because clouds are so complicated and so variable on all space and time scales, they are hard to study, but she always finds beautiful creative ways to "isolate" single problems to be able to study and understand them in detail. <br /><br /><i>She also said that it's possible that having more and more smaller water droplets may make it harder for them to join together for precipitation - though that is not known with any certainty.</i><br /><br />I think that the fact that it is harder to make precipitation with smaller droplets is not that uncertain. Although the quantification surely is difficult. What she probably wanted to say is that it is uncertain how that changes the life time of cloud and what that does to the radiative balance of the Earth. <br /><br />If you have a typical cloud droplet of 10 micrometre, 0.01 millimetre, and a typical rain droplet of 1 millimetre, you see that the difference in size is about a factor 100. That means that the difference in volume is 100*100*100 = 1 000 000. Thus you have to combine 1 million droplets to get one rain droplet. If they are smaller, even more. A further complication is that small droplets have almost no vertical velocity and thus also almost no differences in vertical velocity, which they need to bump into each other. <br /><br />One of the problems which are still not fully understood is how it is possible for a cumulus cloud (a shower) to start producing rain so fast after its first appearance. There are claims that the rain can start within 15 minutes and that is something our cloud models cannot reproduce (without "fudging", for example assuming that there were a few large droplet or dirt particles present already in the beginning, which might be true, but might just as well not be true).Victor Venemahttps://www.blogger.com/profile/02842816166712285801noreply@blogger.comtag:blogger.com,1999:blog-2313427464944392482.post-4910347488190643132014-12-19T03:32:54.174+11:002014-12-19T03:32:54.174+11:00That gave me a smile. Sounds like a fun read.That gave me a smile. Sounds like a fun read.Brandon R. Gateshttps://www.blogger.com/profile/17031044715994785956noreply@blogger.comtag:blogger.com,1999:blog-2313427464944392482.post-11957213553449793112014-12-19T03:25:56.156+11:002014-12-19T03:25:56.156+11:00Ayee, thanks for the legwork on that one, I feel l...Ayee, thanks for the legwork on that one, I feel like I should have been able to find that myself. So the distinction mainly hinges on the time lag between the relatively immediate stratospheric readjustment to radiative equilibrium and the slower surface and trophosphere responses. I think it finally begins to gel for me.Brandon R. Gateshttps://www.blogger.com/profile/17031044715994785956noreply@blogger.comtag:blogger.com,1999:blog-2313427464944392482.post-91631670496230688762014-12-19T02:36:25.659+11:002014-12-19T02:36:25.659+11:00Here is the definition from Chapter 8 of AR5:
The...Here is the definition from Chapter 8 of AR5:<br /><br />The two most commonly used measures of radiative forcing in this chapter are the radiative forcing (RF) and the effective radiative forcing (ERF). RF is defined, as it was in AR4, as the change in net downward radiative flux at the tropopause after allowing for stratospheric temperatures to readjust to radiative equilibrium, while holding surface and tropospheric temperatures and state variables such as water vapor and cloud cover fixed at the unperturbed values.<br /><br />ERF is the change in net top-of-the-atmosphere downward radiative flux after allowing for atmospheric temperatures, water vapour, and clouds to adjust, but with surface temperature or a portion of surface conditions unchanged. While there are multiple methods to calculate ERF, we take ERF to mean the method in which sea surface temperatures and sea ice cover are fixed at climatological values unless otherwise specified. Land-surface properties (temperature, snow and ice cover and vegetation) are allowed to adjust in this method. Hence ERF includes both the effects of the forcing agent itself and the rapid adjustments to that agent (as does RF, though stratospheric temperature is the only adjustment for the latter). In the case of aerosols, the rapid adjustments of clouds encompass effects that have been referred to as indirect or semidirect forcings (see Chapter 7, Figure 7.3 and Section 7.5), with some of these same cloud responses also taking place for other forcing agents (see Chapter 7, Section 7.2). Calculation of ERF requires longer simulations with more complex models than calculation of RF, but the inclusion of the additional rapid adjustments makes ERF a better indicator of the eventual global mean temperature response, especially for aerosols. When forcing is attributed to emissions or used for calculation of emission metrics, additional responses including atmospheric chemistry and the carbon cycle are also included in both RF and ERF (see Section 8.1.2). The general term forcing is used to refer to both RF and ERF. Souhttps://www.blogger.com/profile/08818999735123752034noreply@blogger.comtag:blogger.com,1999:blog-2313427464944392482.post-59660782453361748262014-12-19T02:35:15.435+11:002014-12-19T02:35:15.435+11:00You bet. The hurricane type eddies tracking acros...You bet. The hurricane type eddies tracking across the Atlantic and Pacific were quite cool. Various places where I'd expect wild fires and/or agricultural burning were represented well. Sumatra for instance. I couldn't quite pick out Java in that plume, but I know from experience there is always something on fire in Jakarta. About midway through is a colossal explosion of white stuff in sub-Saharan Africa I can't fathom. An intentional what if, perhaps.Brandon R. Gateshttps://www.blogger.com/profile/17031044715994785956noreply@blogger.comtag:blogger.com,1999:blog-2313427464944392482.post-5704584639183067682014-12-19T02:14:03.583+11:002014-12-19T02:14:03.583+11:00Thanks, Brandon. I've added it to the article....Thanks, Brandon. I've added it to the article. You can see lots in the video. I noticed the bushfires in Victoria (SE Australia) show up really strongly.Souhttps://www.blogger.com/profile/08818999735123752034noreply@blogger.comtag:blogger.com,1999:blog-2313427464944392482.post-59973027182595149642014-12-19T01:38:54.513+11:002014-12-19T01:38:54.513+11:00PS, not to be missed, GEOS-5 aerosols in motion. ...PS, not to be missed, GEOS-5 aerosols in motion. I knew there had to be one: https://www.youtube.com/watch?v=oRsY_UviBPEBrandon R. Gateshttps://www.blogger.com/profile/17031044715994785956noreply@blogger.comtag:blogger.com,1999:blog-2313427464944392482.post-45562852257316997492014-12-19T01:29:12.820+11:002014-12-19T01:29:12.820+11:00Sou,
Gosh that GEOS-5 aerosol image is fascinatin...Sou,<br /><br />Gosh that GEOS-5 aerosol image is fascinating. I need a poster of it, stat. Interesting to see climate engineering with cirrus clouds featured. Do you have any sense of how that portion of her lecture was received?<br /><br />Skipping down to the AR5 radiative forcing chart, I think my brain almost understands the distinction between RF and ERF but I'm not sure I grok it completely. How I would say it is that RF is the straight up direct effect, ERF is like a net effect after interactions with other things in the system. Is that about right?Brandon R. Gateshttps://www.blogger.com/profile/17031044715994785956noreply@blogger.comtag:blogger.com,1999:blog-2313427464944392482.post-70413749942142231382014-12-19T01:03:27.942+11:002014-12-19T01:03:27.942+11:00Anyone interested in clouds could do worse than re...Anyone interested in clouds could do worse than read 'The Cloudspotter's Guide' by Gavin Prector-Pinney (2006). Brilliant layperson introduction to both the aesthetics and science of clouds.<br /><br />You might even consider joining the 'Cloud Appreciation Society' (Gavin is the founder). One of their manifesto pledges is "to fight 'blue-sky thinking'". Who could argue with that?<br />David Rhttps://www.blogger.com/profile/13842200092197524120noreply@blogger.com