Climate Modeling Homework 3 http://www.atmos.washington.edu/2008Q2/559/hw3.html Group 1: change cloud drop number at 1XCO2 : Kyle & Stuart Group 2: change cloud drop radius at 1XCO2  : Kai-Chieh & Rei Group 3: change ice sedimentation rate at 1XCO2 : Silje & Steve Group 4 : change cloud drop number at 2XCO2 : Kelly & Paul Group 5 : change cloud drop radius at 2XCO2 : Ty & Justin Group 6 : change ice sedimentation rate at 2XCO2 :  Kevin & Ed

Each member of the group should do a test run of a couple of days for the cloud drop number experiment at 1XCO2. Then one member should do the run that is assigned to your group above for 10 yrs. The other should run the CAM diagnostics on the last 5 yrs and add a link near the top of the project wiki. The runs will not be long enough for publication quality, but you'll get the big picture results just fine.The poorest accuracy will be in the high latitudes. Each person must turn in answers to EACH question below using the links to the CAM diagnostic on the wiki from all 6 groups. Your answers should be about 3 pages of text total. The instructors know what changes to expect when the experiments are compared to the baseline control. But we are not entirely sure how tinkering with the model in this way will alter climate sensitivity. So it will be a learnng experience for us all. Detailed instructions for executing the experiments are on the project wiki at https://www.atmos.washington.edu/twiki/bin/view/Main/CloudEffectsProject 1. Experiment 1 reduced the cloud drop number without changing the effective droplet radius (the radius used in the radiation calculations). The cloud microphysics package will then allow cloud droplets to grow larger (r3l radius) and hence quickly reduce the amount of cloud condensate (why?). For the 1XCO2 case, discuss the effect on cloud liquid water path (ie the integrated cloud liquid condensate), where are the changes largest and why? cloud amount, why is LWP so different and yet cloud amount changes modestly? longwave and shortwave radiative forcing, why are the differences so puny? planetary albedo, why are the differences so puny? surface temperature (yawn) (All fields are in set 5&6, with zonal means for most in set 3. Use both maps and zonal means for your analysis as needed.) 2. Experiment 2 reduced the cloud drop effective radius over the oceans and sea ice, which only affects the radiation scheme. The amount of condensate is then changed only through cloud (feedback) process with radiation, dynamics, etc (indirect as compared to the more direct consequences in exp 1). For the 1XCO2 case, discuss the effect on the following keeping in mind the perturbation is only over the oceans and sea ice cloud ice water path, why is it generally smaller south of 40 deg and bigger north of 40 deg? cloud liquid water path, this is messy outside of the polar regions. Don't worry about it too much. cloud amount, how have they redistributed vertically at various latitudes? longwave and shortwave radiative forcing, explain in terms of the previous fields as much as possible planetary albedo, explain in terms of the first three fields as much as possible surface temperature 200mb temperature 3. Experiment 3 raised the ice crystal sedimentation rate.  For the 1XCO2 case, discuss the effect on cloud ice water path, why is it generally smaller south of 40 deg and bigger north of 40 deg as before? cloud liquid water path, this is very messy so again don't worry about it too much. cloud amount, what elevation has the biggest change and why? longwave and shortwave radiative forcing, explain in terms of the previous fields as much as possible planetary albedo, why so little change? surface temperature 200mb temperature 4. Make a table of the climate sensitivity for the unperturbed model and for each of the 3 experiments. Discuss why & how the cloud model perturbations altered climate sensitivity.

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