Abstract:Drought-induced reduction in ecosystem production prevails globally and is expected to increase with future climate change scenarios. Understanding spatio-temporal distributions of meteorological drought is fundamental for drought disaster prevention and management, food security, and ecological balance. A standardized precipitation evapotranspiration index (SPEI), derived from the difference between the precipitation and reference evapotranspiration, was used to quantify drought events and consequently reveal the spatio-temporal variation of drought across Northeast China. SPEI at four lags (1, 3, 6, 12 months) was calculated from daily records of mean temperature, daily precipitation, atmospheric pressure, wind speed, relative humidity, and sunshine duration. These climate variables were measured at 90 meteorological stations in Northeast China during 1961-2014. Based on the monthly SPEI values (SPEI01) of each climate station, drought events and disaster were investigated and grouped. Temporal variations of drought events in moderate, severe, and extreme grades were investigated by annual occurrence times, seasonal occurrence ranges, and intensities. Spatial characteristics of meteorological drought in each class were quantified by frequencies of drought events, duration times, and intensities of drought disasters. To analyze the effects of time scale on the drought spatial distribution, the principal modes of variability of the SPEI at four time scales were identified using the empirical orthogonal function (EOF) method. Our results indicated that both interannual and seasonal droughts showed obvious variations across the study area during the period. Interannual drought fluctuated, called "dry-wet-dry-wet" from 1961 to 2014, and was associated with three turning year points of 1983, 1995, and 2008. Seasonal drought appeared more intensive and widely distributed in summer, whereas it was weaker with a smaller distribution range in winter. Drought frequency ranged from 15.2% to 19.2% over the study area. The average drought frequency for moderate, severe, and extreme drought grades was 10.61, 5.2, and 1.2%, respectively. The duration of continuous drought disaster ranged from 2 to 9 months, and the intensity of drought disaster ranged from -8.8 to -3.7. Spatial heterogeneity and complexity of drought were observed in Northeast China. The western region was the most seriously affected area, with the highest drought frequency. The EOF results showed that there were three main spatial modes for drought in Northeast China. The explained variance of the three leading EOFs ranged between 57 and 58.9% as the time scale for calculating the SPEI increased from 1 to 12 months. The explained variance of EOF1 ranged between 37.4 and 39.4%, and the explained variance of EOF2 and EOF3 ranged between 10.6 and 13.1%, and 6.5 and 8.8%, respectively. The spatial coefficients of the EOF1 for all SPEI time scales showed a similar pattern, with spatially uniform variation over Northeast China. Based on the spatial distribution of the spatial coefficients of EOF2 at all SPEI time scales, we identified two homogenous regions:the southern and northern halves of Northeast China. Eastern and western parts of Northeast China were delimited by the spatial coefficients of EOF3. The spatial heterogeneity and temporal variation was more obvious as the time scale increased from 1 to 12 months. The results of this study provided valuable insights for early drought prediction and establishing ecosystem disaster management systems in Northeast China.