I'm investigating the possibilities of rain or snow on Mars. The
possibility is generally discounted because of the low amounts of
water vapor in the Martian atmosphere, from 10 to 100 precipitable
microns, and around 20 precipitable microns on average.
But I was thinking the amount of precipitation that might fall over
some time period might be much higher than the amount of precipitable
water vapor present.
For instance on Earth the maximum amount of precipitable water vapor
is around 5 to 6 precipitable centimeters, 2 to 3 inches, even over
the oceans. Yet during storms you can have very many inches of rain or
snow fall in a single day.
One way this can happen is easy to imagine, even if the precipitable
water within clouds is also below 6 pr. cm. You could have all the
water in a column fall to the ground, then the cloud move so all the
water in another column falls on the same space on the ground. If the
cloud is large in horizontal extent and moving slowly quite a bit
could fall at the same location on the ground.
However, I was also wondering if is possible that the condensed water
amount in a cloud could itself be much higher than 6 pr. cm. even if
the water vapor content in the surrounding cloud-free area is still at
6 pr. cm and below.
Anyone know if this is possible?


Bob Clark