1. Understanding 0Z maximum in the diurnal cycle of rainfall from electrified showers Chuntao Liu Mar, 2009

2. Problem: why is there a maximum of rainfall from electrified showers at 0Z? Note: electrified showers are defined by PFs with t_maxht30dBZ < -10C over land < -17 C over ocean and NO flash.

3. Assumption is something wrong with the programming on the bins used. Used a different program and different bin centered at 0.5, 1.5 …(dashed line) result shows about the same Different approach to explain the 0z maximum is to calculate the variations at different longitude bins (10 degree) and create 2-D variation During 0Z-1Z, there are maxima over west Pacific, Atlantic oceans. There are maxima at 0Z over Africa and America land as well (see next slide). PFs here do not have lightning. And Tmax30dbz < - 10 over land, < -17 over ocean.

4. Further to show 2-D longitude- time volumetric rainfall from electrified showers by separating over land and ocean. The figure is created by volumetric rainfall from electrified shower over land. Then divide by the mean volrain fall from all longitude- hour bins. Over land, the variation is larger. However, because the electrified showers are mainly from ocean, the lower panel contribute more to the figure in the last slide. Note here, over land, there are maxima of volumetric rainfall at 0Z-1Z ( difficult to understand ). PFs here do not have lightning. And Tmax30dbz < - 10 over land, < -17 over ocean.

5. This is mainly from tropics Again, very hard to understand, I am nearly convinced that this is my programming problem. However, I am confident that it is not.

6. For comparison, the group of systems with flash is shown. Certainly, the volrain is mainly from thunderstorms over land. The diurnal cycles seems reasonable over land. However, there seems little dips at 0Z-1Z over Africa and America in this category. This is very interesting. What makes the PFs without lightning over land at 0Z- 1Z???? At the moment, I do not have any answer. PFs here DO have lightning. And Tmax30dbz < -10 over land, < -17 over ocean.

7. Where are those electrified showers at 0Z-1Z? More rainy (brown & purple) electrified showers at 0Z-1Z Three panels are using same categoriza tion values

8. Where are thunderstorms at 0Z-1Z? Less thunder- storms at 0Z-1Z

9. Summary By writing a very different program and using different hour bins, the results are the same. This gives me confidence that the maximum of volumetric rainfall from electrified showers at 0Z is there. This 0Z-1Z maximum is dominated by west Pacific. However, the maxima of electrified rainfall at 0Z exist over land as well. It is interesting that there seems dips of volumetric rainfall at 0z-1z from thunderstorms over land.

10. Possible artifacts leading to 0Z problem NCEP reanalysis is model guided products, 0Z is closer to observations, output at other times are more depending on the model forecast. Here t_maxht30 is estimated using NCEP data. If there is a 0Z bias from NCEP, we might have problem. However, thunderstorms definition has nothing to do with NCEP. So this imagined NCEP bias can not explain less thunderstorms at 0Z. Another bias could from LIS, if LIS tends to detect less efficiently at 0Z for whatever reason, it could lead to adjust some thunderstorms into electrified showers. The last possibility is TRMM sampling more or less at 0Z-1Z.

11. To test if NCEP bias is a factor here. PFs with maximum height of 30 dBZ greater or equal to 6.5 km (about -10C over tropics) and without flash is tested here. 1)0Z-1Z maximum is still there. So this is not caused by the NCEP. 2)Patterns are very close to that using t_maxht30, though without consideration of separation of land and ocean

12. Bias due to LIS detection? From the diurnal cycles of flashcounts, we do see there is a minimum of flashcount at 0Z-1Z. However, this does not seem like an obvious abnormal to me. Further, the minimum is at 4- 5 z.

13. I do not see sampling bias at 0-1Z from this figure, which including all PFs categorized by rain volume

14. What lead to 0Z ? If I have to pick a possible bias, I incline more to bias from LIS than NCEP and TRMM sampling. If there is no bias, then 0-1Z is real. We have to explain why there are more electrified showers at 0-1Z and why there are less thunderstorms at 0-1Z. Why!!!!!!!!!!!!!!!!!!!!!  Our wild imaginations are needed…

15. I DO NOT WANT TO IMAGINE!! Let’s chase down to LIS problem A simple method is to check the histogram of LIS viewtime of each PFs for each hourly bin. If viewtime has a meaningful value, the LIS gives good observations.

16. 0z-1z have less samples with good lightning observations after the boost. (The first peak is for before boost, the second is for after the boost)

17. Problem with LIS, when did that happen? About 10-11/2003

18. There must have been a bug in LIS processing in the current version after near the end of 2003!!!! Problem found !!!!! Now let’s redo the curves only using 1998-2003 data

19. Yeah! 0Z disappeared

20. Yeah! 0Z disappeared Not over land anymore!!!

21. Yeah! Even better match from thunderstorm rainfall!

22. LIS data has problems after 2003 I am so happy not having to explain the weird 0Z problem. This is good, because we have identified a bug in LIS data. Earle, now you can call me “the wizard of 0Z”