# How is deposition mechanism considered in extreme high temperature

**URL:** <https://forum.cmascenter.org/t/how-is-deposition-mechanism-considered-in-extreme-high-temperature/4226>\
**Category:** Chemistry and Aerosols\
**Created:** [July 9, 2023, 2:38pm UTC](https://forum.cmascenter.org/t/how-is-deposition-mechanism-considered-in-extreme-high-temperature/4226 "2023-07-09T14:38:55Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![wangnan](https://avatars.discourse-cdn.com/v4/letter/w/f05b48/32.png) [@wangnan](https://forum.cmascenter.org/u/wangnan)\
**Post date:** [July 9, 2023, 2:38pm UTC](https://forum.cmascenter.org/t/how-is-deposition-mechanism-considered-in-extreme-high-temperature/4226/1 "2023-07-09T14:38:55Z")

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Hi, I would like to inquire about the mechanism of dry deposition in the CMAQ model. Does the model consider the impact of vegetation stomatal closure under extreme high temperatures on dry deposition? How is this mechanism accounted for in the model?

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**Author:** ![wangnan](https://avatars.discourse-cdn.com/v4/letter/w/f05b48/32.png) [@wangnan](https://forum.cmascenter.org/u/wangnan)\
**Post date:** [July 11, 2023, 3:02pm UTC](https://forum.cmascenter.org/t/how-is-deposition-mechanism-considered-in-extreme-high-temperature/4226/2 "2023-07-11T15:02:23Z")

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Oh, please show some guidance to me

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**Author:** ![pleim.jon](https://avatars.discourse-cdn.com/v4/letter/p/4bbf92/32.png) [@pleim.jon](https://forum.cmascenter.org/u/pleim.jon)\
**Post date:** [July 12, 2023, 1:22pm UTC](https://forum.cmascenter.org/t/how-is-deposition-mechanism-considered-in-extreme-high-temperature/4226/3 "2023-07-12T13:22:24Z")

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Dry deposition in CMAQ uses the stomatal conductance from the LSM in WRF. We typically use the PX LSM option in WRF. The PX LSM computes the bulk stomatal conductance using the Jarvis method with emperical functions for air temperature, air humidity, soil moisture, and solar radiation. The PX LSM is described in Pleim and Xiu 1995, Xiu and Pleim 2001, and Pleim and Xiu 2003. the air temperature function looks like:

 ![image](https://canada1.discourse-cdn.com/flex027/uploads/cmas/original/2X/1/1c783dae09216a37d8f5436bdc3cfa59dcba2b2e.png)

So you can see that the stomatal function shuts down at extremely high temperatures

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**Author:** ![wangnan](https://avatars.discourse-cdn.com/v4/letter/w/f05b48/32.png) [@wangnan](https://forum.cmascenter.org/u/wangnan)\
**Post date:** [July 14, 2023, 10:37am UTC](https://forum.cmascenter.org/t/how-is-deposition-mechanism-considered-in-extreme-high-temperature/4226/4 "2023-07-14T10:37:08Z")

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Thanks a lot for your prompt reply. It does help ~