Animation of LGP

This animation visualizes some of the core problems of China's agriculture. It displays so-called Length of Growing Periods (LGP) based on a reference crop for the three decades between 1958 and 1988. These LGP estimates are intermediate results from the IIASA China AEZ model (for details of the model algorithm see the AEZ methodology description in this application). Basically, the LGP represents the climate-related growing conditions of a particular grid cell (there are some 374,000 grid cells in the original map from which this animation above was made). It takes into account the local precipitation, temperature profile, sunshine duration, wind speed, and a few other parameters. With these parameters the model calculates the corresponding growing period of a reference crop. This is the time during which this reference crop has enough sunlight, sufficient precipitation and adequate temperature for its growth cycle. For instance, a LGP of 120 would indicate that in one year the reference crop would have a period of 120 days, in which the local climate conditions of a particular grid cell would be adequate.

Basically, the LGP is a core indicator of agricultural suitability. It combines all important climate parameters (however, it does not take into account soil and terrain constraints - which are taken care of in a later stage of the AEZ model). For rain-fed agriculture the LGP must be at least 60 - 90 days. Below that LGP level crop cultivation is usually impossible. With growing periods of 180 days or more double or even triple cropping is possible.

The animation shows that the conditions are relatively stable in the South and Southeast of China, where the LGP is usually in the range of 300 to 330 days. One very obvious "island of stability" is Sichuan. While the LGP is changing frequently in areas to the North, East, and South of Sichuan over the three decades between 1958 and 1988, there was always an LGP above 300 in Sichuan. This - at least partly - explains, why Sichuan was a center of agricultural civilization for thousands of years. The climate conditions in the Sichuan basin - which is surrounded by mountains - are much more stable than in the adjacent areas.

The animation also displays impressively the instability of climate conditions in the border-region between the South-east and the North of China. There is a corridor of heavy fluctuations in the LGP between 1958 and 1988 stretching from the South (Yunnan province) to the Northeast (Heilongjiang province). In this corridor growing conditions changed from year to year. While in some years the LGP was more than 200 days, it was only 120 to 180 in others. Primarily depending on fluctuations in precipitation the rapidly changing growing conditions make the harvests highly unpredictable in this corridor. These modeling results are confirmed by statistics, which show that the annual grain production in these regions varied strongly. It was quite good in some years, but much lower in others.

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