0.5 K/day to 6 K/ day. By increasing the uplift speed, more ice water content and ice crystals form with smaller sizes due to the fact that higher super-saturations are reached before the ice particles can quench excess humidity. Higher super-saturations lead to high ice fractions activated. Figure 6.9: The heating rates (in output time interval 130 or time=325 min) with height in modeled cirrus cloud formed on glassy aerosol particles for different vertical velocities, other conditions are as the same as Figure 6.2. Radiation simulations have been performed with different solar zenith angles to test the impact of solar zenith angle on cloud radiative heating vertical profiles during the day. The solar zenith angle is expected to have a significant effect on the solar radiative properties since this is what some satellite instruments take advantage of to see very thin cirrus clouds that are sub-visible if viewed directly overhead with the sun also overhead. The satellites (such as MODIS) use the fact that these thin clouds can have significant optical paths if the sun is at a grazing angle and can pick up the presence of cirrus for this situation. However, these clouds will still have small radiative properties because the clouds are so thin. So, the radiative heating rate of sub-visible cloud is not expected to be significant even though it may change a lot with different solar zenith angles. Figure 6.10 shows that changing the solar zenith angle factor in the model from 5°, 30°, 60°, and 85° leads to the following cloud solar heating rates of 0.43, 0.68, 0.83 and 0.86 K/day, respectively, and roughly an increase of an order of 0.1 K/day in infra-red heating rate. The IR heating rate is increased because the increased solar heating rate in the layer increases the temperature in the atmosphere and this alters the IR radiative properties which are very
0.5 K/day to 6 K/ day. By increasing the uplift speed, more ice water content and ice crystals form with smaller sizes due to the fact that higher super-saturations are reached before the ice particles can quench excess humidity. Higher super-saturations lead to high ice fractions activated. Figure 6.9: The heating rates (in output time interval 130 or time=325 min) with height in modeled cirrus cloud formed on glassy aerosol particles for different vertical velocities, other conditions are as the same as Figure 6.2. Radiation simulations have been performed with different solar zenith angles to test the impact of solar zenith angle on cloud radiative heating vertical profiles during the day. The solar zenith angle is expected to have a significant effect on the solar radiative properties since this is what some satellite instruments take advantage of to see very thin cirrus clouds that are sub-visible if viewed directly overhead with the sun also overhead. The satellites (such as MODIS) use the fact that these thin clouds can have significant optical paths if the sun is at a grazing angle and can pick up the presence of cirrus for this situation. However, these clouds will still have small radiative properties because the clouds are so thin. So, the radiative heating rate of sub-visible cloud is not expected to be significant even though it may change a lot with different solar zenith angles. Figure 6.10 shows that changing the solar zenith angle factor in the model from 5°, 30°, 60°, and 85° leads to the following cloud solar heating rates of 0.43, 0.68, 0.83 and 0.86 K/day, respectively, and roughly an increase of an order of 0.1 K/day in infra-red heating rate. The IR heating rate is increased because the increased solar heating rate in the layer increases the temperature in the atmosphere and this alters the IR radiative properties which are very
sardar_thesis_Aug_23.docx