January September Npp Global

Fig. 1 shows the daily mean of global NPP for each month in 1998, where Fig. 1-(a) to (l), are corresponding to January to December. It should be noted that one largest El-Nino occurred from the end of 1997 to 1998, and these results could be slightly different from other years. On the land, large values of NPP are obtained in tropical rain forests and savanna as well as boreal forests around 50 to 60 degree north. In the ocean, large values are obtained on the continental shelf regions, like the west coast of Africa, the East China Sea, and the west coast of South Africa during phytoplankton bloom. In the eastern equatorial Pacific ocean, which is known as the equatorial upwelling region, a rather high NPP values was observed. Comparisons from Fig. 1(a) to Fig. 1(l) exhibit a large seasonal change on a local scale.

Fig. 2(a) shows a monthly change of zonal mean of NPP. The highest values are obtained in September to October at 10 to 0 degree north. These areas correspond to the northern part of South America, a savanna in Africa, and a part of Indonesia and Malaysia. These seasonal increases of

Figure 1: Global NPP maps in 1998. (a) January, (b) February, (c) March, (d) April, (e) May, (f) June, (g) July, (h) August, (i) September, (j) October, (k) November, (l) December (For colour version, see Colour Plate Section).

Figure 1: Global NPP maps in 1998. (a) January, (b) February, (c) March, (d) April, (e) May, (f) June, (g) July, (h) August, (i) September, (j) October, (k) November, (l) December (For colour version, see Colour Plate Section).

(i)
Latitude

Longitude

0 180 360

Longitude

0 180 360

Figure 2: Seasonal change of zonal and meridional mean NPP. (a) Zonal mean. Horizontal axis corresponds to 80—80 degree from north to south and vertical axis corresponds to January to December. (b) Meridional mean. Horizontal axis corresponds to 0-360° eastbound and vertical axis corresponds to January to December (for colour version, see Colour Plate Section).

Figure 2: Seasonal change of zonal and meridional mean NPP. (a) Zonal mean. Horizontal axis corresponds to 80—80 degree from north to south and vertical axis corresponds to January to December. (b) Meridional mean. Horizontal axis corresponds to 0-360° eastbound and vertical axis corresponds to January to December (for colour version, see Colour Plate Section).

NPP may correspond to rainy season in these areas. High NPPs are next obtained in June to July at 30-50 degree north. These areas cover most of the large crop field in the North America and the Eurasia, which correspond to agricultural fields and exhibit a distinct seasonal change. In contrast, the regions from 10 to 20 degree north and 0-20 degree south show rather high NPP with very weak seasonal changes, where tropical forests are major contributors with weak seasonal changes.

Fig. 2(b) shows a monthly change of meridional mean of NPP. The highest values are obtained in May to July between 30 and 40 degree east, where the eastern part of Western Europe, some part of savanna, and some part of tropical forests are included. As tropical forests show very weak seasonal change as discussed in a zonal mean of NPP, the seasonal change observed between 30 and 40 degree may be the result of the change in savanna and agricultural fields in Europe. This seasonal change is also evident between 0 and 30 degree east, where the western part of Europe could be a major contribution. Next high NPP regions are observed from June to August between 100 and 120 degree east, which covers the most of the South Eastern Asia and exhibits high seasonal variations, because of agricultural fields in this region. The North and South America also show high NPP values, which is corresponding to the region between 110 and 40 degrees west. The North America shows high seasonal variations, i.e. high NPPs in May to September. South America, however, shows a small seasonal change because of tropical forests in this region.

However, it should be noted again that NPP in 1998 was influenced by a large El-Nino event. Therefore the Western part of the American continent had high-level precipitations, while Indonesia suffered from drought. Also, NPP in the equatorial Pacific was rather small because of reduction of equatorial upwelling in this zone.

Was this article helpful?

0 0

Post a comment