Please help regarding plotting the Intertropical Convergence Zone (ITCZ) on a map.
There is a lot of ITCZ data available at SSMI http://www.ssmi.com/ssmi/ssmi_browse.html - You can visualize the ITCZ in cloud water or rain rate (for example) in their pre-rendered data.
I've successfully managed to plot the ITCZ using data on the "high cloud fraction". The best product to use is probably from the MODerate-resolution Infrared Spectroradiometer (MODIS instrument), which can be obtained as gridded version 3 datasets, or interpolated to gridcells yourself. You'll be able to hold of cloud top pressures, and can assume that below p = 300 hPa (or see the International Cloud Climatology Project (ISCCP) for a better definition) is a suitable level for high clouds. The version 2 individual sensor footpring data can give you sub-gridcell information, such as the proportion of cloud-tops below 300hPa that are classified as high.
Since high clouds are most frequent at the tropics, you'll see higher fractions over the equator - although it is a pretty discontinuous band so you may have to tweak your high cloud threshold to lower altitudes (higher pressures). One can usually assume that the highest high cloud fraction within a latitudinal gridcell is close to the centre of the ITCZ. A better method that I tried is to find the median value, that lies at the half way point when tallying up all the high cloud fractions from the north to south pole.
Hope that helps.
Chris
Dear Andersen and Nankervis, I thank you alot for dedicating your time to reply to my querry. I could not fine data at www.ssmi.com neither was I able to understand how to use modis data. I would request you to send me the shapefile of global ITCZ if you have. I shall be highly indebted. Also I would encourage if i get some paper giving detailed methodology of how to plot ITCZ using any data for that matter.
Once again thankful.
Mahjoor
www.cci-reanalyzer.org
Mahjoor, you can use the link above to plot various reanalysis metrics that can be used to show the ITCZ position. that and other online tools and data (like those provided by NOAA e.g.. 20CRv2 or NCEP1) are easy to access if you do a google search for 'reanalysis data plotting online'
for convective regions, I like using either OLR or vertical velocity (Omega)...I also have used precipitable water or cloud cover too, but the first two probably give a better approximation of the actual maximum convective line. We outlined some of these metrics in the SPCZ reconstruction paper you can see on my contribution page here on Reserach gate.
Dear Andrew
Thank you so much for the link. This indeed is very useful. I will try to exploit the maximum information I can. In case I need further help, (In other studies too) may I please contact you?
Can you please give doi or title of your SPCZ paper as i see a big list of papers.
I feel highly obliged by your help and would be very happy in case i can ever be of any help to you.
Best regards
Mahjoor
Dear Mahjoor,
Did you find an ITCZ shapefile? If so, would you be able to send it me?
Thanks!!!
Andre
Dear André and Veettil
I am sorry but that is what actually I am still looking for. Since I could not get it that time, I digitized ITCZ from a research paper. However, later I found that wasn't as correct.
So, I am still looking for a shapefile for summer and winter ITCZ. I can do the GIS work if someone can provide the base data.
Please share the shapefile of the same if you get a hand on it.
Best regards
Mahjoor
Thanks for your answer Mahjoor! I will keep looking for it and will let you know if something comes up.
Regards,
Andre
Dear Mahjoor,
Did you find an ITCZ shapefile? If you did, could you send it to me?
Best regards
Zahra
Dear Zahra Okba,
I needed this ITCZ shapefile during my Ph.D. I found a lot of discrepancies between different ITCZs plotted by various researchers, I chose one published in a reputed journal and plotted it in a GIS environment. I would have been more than happy to share, but I lost the file. I am too occupied by various assignments but considering the number of requests I am getting for the ITCZ shapefile, I will find time in the near future and plot it to share with all. If you are not concerned about the geographic coordinates, then you can just trace it using any image editing software, like CorelDRAW, Adobe Illustrator, etc.
Another method to plot ITCZ is based on atmospheric pressure/ wind during monsoon (Like July) at 850 hPa. (If you do this, please explain to me too, lol)
Cheers
Mahjoor
Dear Mahjoor,
Thank you so much for your feedback! the geographic coordinates are essential for my thesis research I can't just edit it in some editing software, If you found the file in near future I will be glad to receive it.
Best regards
Zahra
Zonal mean streamfunction vertically averaged at the latitude closest to the equator.
For more information can be found in Byrne & Schneider (2016)
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