Remote Sensing for Malaria by Felix Kogan

Author:Felix Kogan
Language: eng
Format: epub
ISBN: 9783030460204
Publisher: Springer International Publishing

(6.3)

(6.4)

(6.5)

where a is a coefficient, changing from 0 to 1 and showing a contribution of VCI and TCI into the total Vegetation health (VHI).

If malaria-VH model is developing for an area, where disease data are collected, then VCI, TCI and VHI weekly 4 km2 data are aggregated over the modeling area for each week and year as mean spatial values. Example of such weekly data during 1982–1998 are shown on Fig 6.3b. Even preliminary analysis comparing dM and IVH indices indicate that, for example, very large number of malaria cases in 1983 (dM = +0.78) were related to favorable thermal conditions (TCI = 76) and excessive moisture conditions (VCI = 60). Even combine index (moisture-thermal) shows healthy vegetation conditions for spreading malaria (VHI = 60). However, further analysis includes an investigation of relationship between the annual number of malaria cases (deviation from trend, dM) with each week’s VCI, TCI and VHI during the years of malaria data. The goals were to test if dM-VH (VCI, TCI, VHI) relationship is strong during malaria season and the critical period (a period of the strongest malaria response to changes in weather conditions). In addition, since the critical period continues for a few weeks in a row, all these weeks might show a strong dM -VH correlation (no jumps between the neighboring weeks). An inclusion of all these weeks in the regression models is not advisable, since the independent weekly variables (VH indices) are highly collinear (correlate strongly with the neighboring weeks’ VHs). Therefore, two types of dM models were investigated: (a) with the independent variables for the week with the highest Pearson correlation coefficient (Eqs. (6.6)) or combining several weeks’ indices (during the critical period) with Pearson correlation coefficients (CC) greater than 0.5. In the second case, the mean indices values for the selected weeks were used as the independent variables (Eqs. 6.7).

Download

Copyright Disclaimer:
This site does not store any files on its server. We only index and link to content provided by other sites. Please contact the content providers to delete copyright contents if any and email us, we'll remove relevant links or contents immediately.