FOUR United States warships returned to Hongkong yesterday for their second visit in six months, after taking part in two very different military operations. The aircraft carrier USS Kitty Hawk, frigate USS Jarrett and cruisers USS William H. Standley and USS Cowpens, arrived for a five-day visit after seeing action in the Persian Gulf when coalition forces attacked Iraq in January. The battle group was also involved in the United Nations relief efforts in famine-stricken Somalia. After sailing from Hongkong to the Gulf last December, the ships were diverted to the coast of Somalia in order to provide air support for the US Marines and coalition forces involved in Operation Restore Hope, the campaign to provide food and medical supplies in the African country. A company of about 80 Marines, based on board the Kitty Hawk, landed in the country to help secure supply routes for the international aid agencies. In January, the vessels moved into the Persian Gulf and 35 aircraft from the Kitty Hawk staged an air strike against an Iraqi missile site. Tomahawk cruise missiles from the Cowpens scored direct hits on a suspected nuclear weapons research installation near Baghdad. ''These missions to Somalia and Iraq were completely different but equally as important,'' said Lieutenant Rob Newell of the Kitty Hawk. ''They demonstrated how adaptable we have to be.'' The ships were relieved by the USS Nimitz and its battle group last month. The replacement force also visited Hongkong on its way to the Middle East. The Cowpens, Jarrett and William H. Standley are docked at HMS Tamar in Central. It is likely to be the last time that the US Navy will use the British naval base before it moves to Stonecutters Island next month. A spokesman for the British Garrison said the Americans would be using dock facilities at the new base, although there may be insufficient room for the three ships. A group of wives and girlfriends were waiting to greet their loved ones as they stepped on to Hongkong soil. The Kitty Hawk will remain anchored off Green Island until Saturday, when the group leaves for its home port of San Diego, California.