Also artillery have longer range when fired from hi altitude to lo altitude.Take a look at map below

http://zzwave.com/plaboard/posts/3962168.shtml --Better still,equip them with glider warheads

Link: China deploys long-range rocket launcher ‘as deterrent to India’ | South China Morning Post (scmp.com)

"The modular rocket system of the PCL-191 is able to carry eight 370mm rockets, each with a range of 350km (220 miles), or two 750mm Fire Dragon 480 tactical ballistic missiles, each capable of flying up to 500km, according to Modern Ships..."