Southern Alps. Simulated 3D high-altitude panoramic view of the Southern Alps on New Zealand's South Island, viewed from the southwest. Image based on Landsat satellite images and detailed digital terrain data. Prevailing winds from the Tasman Sea to the west bring moisture to the mountains, making them quite green, but leave a dry rain shadow across the rest of the South Island to the east. The brightest of the lakes are glacier-fed, their waters appearing azure due to suspended glacial dust. In the distance lies the Pacific Ocean and New Zealand's second largest city, Christchurch.