If the topography is flat other then the craters, you would have environment temperature be based on distance from the poles, and closeness to the equator. The flat surface would lead to massive winds as well, with nothing to divert the pressure you might create a vacuum that would be devastating to most life. Assuming those winds do not exist:
On earth, you often have deserts and jungles form from the excess of (or lack of excess) moisture. Usually you see this occurring by mountain ranges, one side will end up dry because the moisture is held to one side of the mountain. If everything is flat except for the craters, the growth of vegetation and life would be focused around the pools where precipitation is more likely to occur.
Even though 50% is water, nothing is requiring the pools to be evenly spread, so I see huge amounts of land with few pools becoming the deserts and tundra due to lack of moisture. Tundra near the poles, and warm deserts the closer you get to the equator. Similarly, the region with the densest pool amount would create the jungles. These places would likely be wet, and rain at least once a day like the rain forests of Brazil and Africa. Moderate spreading of pools would result in a traditional forest, and the further you go from the equator towards the poles the forests would transition to having tropical plants, to having deciduous plants, to having a Taiga biome.
Plains would exist between the deserts and the forests, but as a transitional biome, most of their water would likely be rains pushed from the jungle/ forests.
check out this site to see how and why biomes on earth formed the way they did: