Both Sides Now 20 March 2016 by Leslie Hartten (CIRES)<\/p>\n
![](\"http:\/\/ciresblogs.colorado.edu\/el-nino-rapid-response\/wp-content\/uploads\/sites\/51\/2017\/01\/1CwILtzqGS5JCilHy3Lu32A.png\")
(Left) View to the NNE on 3 March. In the center of the photo, no clouds can be seen below and behind the front cloud because of the rain that\u2019s falling from it. (Right) View to the NE about 3 hours after the 18UTC north Pacific surface analysis that shows the ITCZ just north of Kiritimati Island. (Credit: Leslie Hartten,\u00a0CIRES)<\/p>\n
20 March 2016by Leslie Hartten (CIRES)<\/p>\n
![](\"http:\/\/ciresblogs.colorado.edu\/el-nino-rapid-response\/wp-content\/uploads\/sites\/51\/2017\/01\/19uAURkXTXDM8vzuvS3nCQw.jpeg\")
A conceptual picture of the general circulation features of the earth\u2019s atmosphere, including the ITCZ. Fig. 7\u20136 from Ackerman and Knox, Meteorology: Understanding the Weather,\u00a02015.<\/p>\n
KIRITIMATI ISLAND, Kiribati\u200a\u2014\u200aThe Intertropical Convergence Zone. The ITCZ. Every student in an introductory meteorology class learns about it. It\u2019s the region near the equator where the northeast (Northern Hemisphere) trade winds and southeast (Southern Hemisphere) trade winds meet. It\u2019s a phrase and some big puffy clouds on a figure showing the general circulation of the atmosphere. It\u2019s a special line on a surface map, a bright red \u201cZZZZZZZZ\u201d. It\u2019s a long smooth east-west band of rain on a monthly satellite map, or a long broken band on a daily satellite map. Sometimes in the eastern Pacific, there\u2019s a \u201cdouble ITCZ\u201d, two parallel bands of clouds and rain stretching for tens of degrees. Very tidy. Very neat.<\/p>\n
![](\"http:\/\/ciresblogs.colorado.edu\/el-nino-rapid-response\/wp-content\/uploads\/sites\/51\/2017\/01\/1dFjG6S0xsRf2RTEQIwz2Ww.png\")
Daily satellite-based precipitation estimates from early (left) and middle (right) March. Both show a double ITCZ in the eastern central Pacific, with a more unified ITCZ to the west. We recorded about 60mm during the 24 hours shown on the right, and about 90mm in the following 24\u00a0hours.<\/p>\n
But here, on this blip of ground surrounded by the equatorial east Pacific Ocean? What\u2019s the ITCZ?<\/p>\n
It\u2019s hard to pin down. One satellite product said we were in the thick of it; a surface analysis said it was 10\u00b0 to our east.<\/p>\n
![](\"http:\/\/ciresblogs.colorado.edu\/el-nino-rapid-response\/wp-content\/uploads\/sites\/51\/2017\/01\/1S5c990W4newPqliSBPjFnw.gif\")
This analysis from 8am on 20 March (LINT) is the first I\u2019ve seen to actually extend the ITCZ over Kiritimati Island.<\/p>\n
For us, it\u2019s the line of clouds that\u2019s always in view off the northeast coast of the island, where our hotel is. It\u2019s the dark bank of grey to the northeast, half-hidden behind that towering cumulus cloud and the rain shaft beneath it. It\u2019s the 6″ of rain we received on March 17 and 18, and the 15″ our rain gauge recorded in the first 17 days it was up. It\u2019s the gusty winds and the driving the rain into Scott\u2019s face as he worked on filling the balloon, almost smashing the radiosonde package into Alex\u2019s head as he shot video of this afternoon\u2019s launch.<\/p>\n
It\u2019s loud, but not with the thunder many of us expected. Only Paul has heard thunder here, and only once. A look at global lightning data shows that the east Pacific ITCZ has had very little electrical activity during this deployment. Its loudness comes from the waves crashing against the reef, and from the rain beating against roofs and walls and pavement.<\/p>\n
And it\u2019s the spaces. The rain that didn\u2019t fall here, but on the bird sanctuary in southeast Kiritimati. There\u2019s a distance that stays between us and that bank of clouds on many days. The bright sun between showers. The clear atmosphere above cumulus clouds that never got saturated enough to rain.<\/p>\n
Not so tidy. Not so neat.<\/p>\n
I\u2019ll never look at those \u201cbig picture\u201d views of the ITCZ in quite the same way.<\/p>\n
\u201cI\u2019ve looked at clouds from both sides now, from up and down, and still somehow it\u2019s clouds illusions I recall. I really don\u2019t know clouds at all.\u201d\u200a\u2014\u200aJudy Collins<\/em><\/p>\n\n","protected":false},"excerpt":{"rendered":"