Complex sentence: The southern and central parts of the Gobi Desert have variable plant growth due to this monsoon activity, where as the more northern areas of the Gobi are very cold and dry which is attributed to the Siberian-Mongolian high pressure cells.
Split into simpler sentences: The southern and central parts of the Gobi Desert have variable plant growth due to this monsoon activity. The more northern areas of the Gobi are very cold and dry which is unable to support much plant growth, this cold and dry weather is attributed to Siberian-Mongolian high pressure cells.