# Strange behavior on down-welling longwave radiation when the "DO\_LW\_CAL" turned on

**URL:** <https://forum.cmascenter.org/t/strange-behavior-on-down-welling-longwave-radiation-when-the-do-lw-cal-turned-on/1149>\
**Category:** WRF-CMAQ\
**Created:** [November 26, 2019, 11:45pm UTC](https://forum.cmascenter.org/t/strange-behavior-on-down-welling-longwave-radiation-when-the-do-lw-cal-turned-on/1149 "2019-11-26T23:45:46Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![blueingel](https://yyz1.discourse-cdn.com/flex027/user_avatar/forum.cmascenter.org/blueingel/32/394_2.png) [@blueingel](https://forum.cmascenter.org/u/blueingel)\
**Post date:** [November 26, 2019, 11:45pm UTC](https://forum.cmascenter.org/t/strange-behavior-on-down-welling-longwave-radiation-when-the-do-lw-cal-turned-on/1149/1 "2019-11-26T23:45:46Z")

</div>

I recently compared WRF-CMAQ simulations with different feedback options. The version that I used is WRFv3.8-CMAQv5.2. The simulation domain I used is 12US2. I found that strange fragmentation and leaps appear on “LWDNB” (down-welling longwave radiation) and “LWUPB” WRF outputs, when longwave feedback is included in the simulation, e.g., “DO\_LW\_CAL” is turned on. There is no such problem when only “DO\_SW\_CAL” is turned on or on no feedback runs.  
Does it mean that there is a bug in the longwave feedback module?  
Please see the attached figure

 ![PNG](https://canada1.discourse-cdn.com/flex027/uploads/cmas/original/1X/8bb67566813e517198dd759f134a71751832daec.jpeg)

---

<div class="post-metadata">

**Author:** ![blueingel](https://yyz1.discourse-cdn.com/flex027/user_avatar/forum.cmascenter.org/blueingel/32/394_2.png) [@blueingel](https://forum.cmascenter.org/u/blueingel)\
**Post date:** [November 26, 2019, 11:47pm UTC](https://forum.cmascenter.org/t/strange-behavior-on-down-welling-longwave-radiation-when-the-do-lw-cal-turned-on/1149/2 "2019-11-26T23:47:58Z")

</div>

Sorry, the unit should be “W/m^2” instead of “K” for those figures.

---

<div class="post-metadata">

**Author:** ![lizadams](https://avatars.discourse-cdn.com/v4/letter/l/49beb7/32.png) [@lizadams](https://forum.cmascenter.org/u/lizadams)\
**Post date:** [December 9, 2019, 9:22pm UTC](https://forum.cmascenter.org/t/strange-behavior-on-down-welling-longwave-radiation-when-the-do-lw-cal-turned-on/1149/3 "2019-12-09T21:22:27Z")

</div>

Hi,  
I am sorry for the delay in our response.  
Your issue is related to the long wave aerosol direct effect.  
This option has been implemented but not been fully evaluated and is considered a “research option.” Please contact David Wong directly at [wong.david-c@epa.gov](mailto:wong.david-c@epa.gov). He is on vacation, and may not be able to get back to you until he returns.