Air is not heated much by radiation, but it is heated efficiently by direct contact with hot surfaces. I therefore propose that solar air heaters be used for the "base" of the solar updraft towers, rather than greenhouses. With greater efficiency one would not have to have such a large area (the greenhouse needs a huge area). Also, with solar air heaters, the heaters can be mounted vertically, saving huge space. See photo.
President Trump is trying to save oil, gas and coal jobs and so on, so it seems oil is here to stay for a while, in the US anyway. If one could use oil and gas at night to heat water and feed moist air or steam into the solar updraft tower, one could increase the chances of convectional rain. With gas and oil to heat water, the tower could become a steam method electricity generator and rain maker at night. One could heat seawater if one is close to the sea. Trees could be grown in the deserts using this method, making it fairly "green".