Crop planning based on rainfall variability for Bastar region of Chhattisgarh, India

Analysis of long-term rainfall data (1986-2018) of Bastar region revealed decreasing trend in total quantum of annual rainfall with varying frequency and distribution. The quantity of winter and summer rains decreased drastically during 2008-18 as compared to earlier two decades (1986-96 and 1997-2007). SW monsoon rain of 2008-18 was more than past two decades, whereas NE monsoon rain changed much in quantity except during 1997-2007. During 1986-96, the pre-monsoon shower was received in April, but later two decades the shower was received in May, which supports for summer ploughing and dry aerobic seeding. The cropping period almost synchronized between 22-43 standard meteorological week (SMW) reaching 93.11 mm per week as maximum rainfall. As the probability of 20 mm rainfall decreased from 75 to 50%, the crop yield got reduced by 30%. The mid-land rice with a probability of 13.47 to 16.07 mm rain per week supported growth phase during 17-21SMW. Whereas, upland rice maturing in 90-100 days could avoid dry spells, if the rice is managed by conservation furrows at the time of sowing. The summer ploughing is preferred with more than 40 mm rain in single day during March to April for mitigating dry spells. On the other hand, preparatory tillage and sowing were performed together in support of ripening niger and horsegram under probability of 75, 50 and 25% rain through crop planning. Maize and small millets reduced yield significantly when rainfall reached 75% deficit, whereas 25% deficit rain did not affect the yields.

Space- and time-varying associations between Bangladesh's seasonal rainfall and large-scale climate oscillations

Understanding teleconnections of a region's climate can be beneficial to seasonal outlooks and hydro-climate services. This study aims at analyzing the teleconnections of seasonal rainfall over Bangladesh with selected climate indices, including El Niño/Southern Oscillation (ENSO), Indian Ocean Dipole (IOD), Pacific Decadal Oscillation (PDO), and Atlantic Multidecadal Oscillation (AMO) indices. Rainfall data spanning from 1965–2017 in the seven hydrological regions are used to derive three seasonal rains, namely the pre-monsoon (March–May), monsoon (June–September), and post-monsoon (October and November) rains, for correlation- and wavelet coherence (WC)-based teleconnection analyses. Among the three seasonal rains, the post-monsoon rain shows the negative correlations, strongest with the IOD and ENSO indices. Correlations between the pre-monsoon/monsoon rain and climate indices are subject to notable spatial and temporal variations. For instance, correlations between the pre-monsoon (monsoon) rain in the South Central (South West) region and the IOD (ENSO) index shift from negative to positive after the 1980s, whereas the comprehensive negative correlations of the post-monsoon rain with the IOD and ENSO indices further enhanced from the early to recent epochs. WC analysis not only corroborates the findings of correlation analysis at shorter time scales (e.g., 1–4 years), but also reveals significant coherence at longer time scales (e.g., 8–16 years). We find that the pre-monsoon and monsoon rains experience the phase change in WC from shorter to longer scales. In contrast, the post-monsoon rain shows the consistent anti-phase WC, more dominant at the longer time scale. Both correlation and WC analyses indicate that the association patterns of the PDO mimic those of ENSO. Lastly, the analysis results of the AMO suggest quite distinct and significant association between Bangladesh's rainfall and the Atlantic Ocean.

Waterworks

An excerpt from Ibn Baṭṭūṭa introduces the challenges of surviving in this arid region. All the existing Indian methods for harnessing and storing monsoon rain were employed in Bayana, adapted and enhanced by the Muslims, resulting in a variety of dams, wells and reservoirs. The reservoirs vary from enhanced natural depressions, such as the “Peacock Lake” planned to supply the Fort, to the more elaborate reservoirs with steps at all sides (bā’olīs). All significant remains are surveyed, notably the Jhālar Bā’olī, an elegant walled and colonnaded structure built in 1318 by the Khaljī governor, Kāfur Sulṭāni, possibly for the army campground but exceptional in its design and creation of a micro-climate. The deep rectangular bā’olīs with a well at one end and steps at the other could also have shady underground arcades and colonnades as places of resort from the heat: the Bā’olī of Khān-i Khānān built for the use of Hindus in the Fort has a hierarchy of space and ornament anticipating early Mughal buildings, other step-wells combining pleasure and utility include that at Barambad, in the garden of Maryam Zamānī, the wife of the Emperor Akbar.

Rediscovery of Aeschynanthus monetaria (Gesneriaceae) in Southeast Tibet, China after more than 100 years

Aeschynanthus monetaria, a beautiful epiphytic species of Gesneriaceae, was rediscovered in monsoon rain forest along the Yarlung Zangbo River in Motuo County, Southeast Tibet (Xizang), China. Its description is amended and completed with both fresh and dried specimens in this discovery. To better facilitate its identification, the color images in the field and line illustrations based on our specimens are given. A taxonomic note concerning its lectotype and the ending of specific epithet is discussed.

Climate Change-Resilient Rice Production Technology: A High Yielding, Water Efficient and Remunerative Option for South Asian Farmers

Rice (Oryza sativa L.) production in South Asia is increasingly threatened by the erratic nature of onset of monsoon rain and climate change. Wide variance in rainfall pattern affects the timing of nursery raising and transplanting later in the main field. Existing rice cultivation practices such as direct seeded rice using drum seeder (DSR), system of rice intensification (SRI) and conventional transplanting (CT) are not able to address the production problems adequately. Therefore, we developed a package of practices - Climate Change-Resilient Rice Production Technology (CRRPT) - which allows keeping rice seedlings in the seedbed for an extended period to synchronize with the onset of monsoon rain. On-station trials during 2015-2016 comparing CRRPT with DSR, SRI and CT demonstrated that in CRRPT the seedlings can be maintained successfully in the seedbed for up to 55 days while achieving the equivalent yield of CT (30 days seedling) because of improved plant vigour. The CRRPT seedlings of 25 d and 35 d gave 22% and 11% more yield compared to CT (30 d seedling). Total water requirement in CRRPT was reduced by 20%, 14% and 13% in case of 55d, 45d and 35 d seedling, respectively, compared to that for CT (30 d seedling). In an on-farm study with 120 farmers’ fields in West Bengal during 2017-2018, average yield increased by 32% and net profit increased by 96%. Thus, CRRPT is remunerative, water efficient, climate change-resilient and can be easily adopted in the farmers’ fields. Results demonstrate that there is wide scope for its adoption for sustainable rice production in West Bengal and South Asia.

Microphysical Features of Rain and Rain events during different Seasons over a Tropical Mountain location using an Optical Disdrometer

In the present study, seven-year-long observations of rain microphysical properties are presented using a ground-based disdrometer located at Braemore; a site on the windward slope of the Western Ghats (WG) over the Indian Peninsula. The annual cycle of rainfall shows a bimodal distribution with a primary peak during summer monsoon and secondary peak during pre-monsoon. Pre-monsoon rain events are less in number but are with high intensity and characterize large raindrops and low number concentration. During summer monsoon, short and less intense rain events with small drops are noticed. Post-monsoon rain is having a long duration less intense events with lower concentration of large raindrops compared to the summer monsoon. In the seasonal variation of mean diameter (Dm) and raindrop concentration (NT) with Rain Intensity (RI), winter and pre-monsoon rains exhibit higher values of Dm and lower values of NT compared to the summer and post-monsoon seasons for all the RI ranges. The mean features of the rain microphysical parameters are also supported by the case studies of rain events. RI, Dm and NT are categorized into different range bins for all the seasons to identify their variation and relative rainfall contribution to the total seasonal rainfall. Heavy drizzle/Light rain has maximum rain duration, and the relative contribution to the rainfall is high from heavy rain type. Winter and pre-monsoon rains are mostly contributed from the larger raindrops (>Dm3), and during summer and post-monsoons it is from Dm2 onwards. The distribution of occurrence frequency of NT and rainfall are similar during all four seasons. NT2 recorded rainfall percentage nearly the same as NT1 in summer monsoon and this also supports large number of raindrops in this season. In RI-Duration analysis, all seasons showed similar distribution, and 90% of total duration is contributed from RI with less than 20 mm h−1.

Influences of Tropical Indian and Pacific Oceans on the Interannual Variations of Precipitation in the Early and Late Rainy Seasons in South China

Because of the seasonal northward migration of the East Asian summer monsoon, the mean-state atmospheric circulation in South China (SC) is remarkably different between the early (May–June) and late (July–August) rainy seasons. This study presents distinct teleconnections between the SC precipitation in the two periods and the sea surface temperatures (SSTs) in the tropical oceans. In the early rainy season when the major monsoon rain belt is located in SC, the increased local precipitation is related to the tropical Indian Ocean Basin warming. The basin warming induces an anomalous anticyclone in the South China Sea–western North Pacific (SCS-WNP). The related southwesterly anomalies transport more moisture to SC and lead to more moisture convergence and precipitation there. In the late rainy season when the major monsoon rain belt migrates northward to the Yangtze River valley, the precipitation increase in SC can be caused by the dipole SST anomalies in the tropical Pacific with the cold anomalies near the Maritime Continent and warm ones near the date line. The dipole SST anomalies generate an anomalous cyclone in the WNP with its center more northward than that of the anomalous anticyclone in the early rainy season. The related northeasterly anomalies along its northwestern flank reduce the climatological northward transport of moisture flux out of SC, and increase the moisture convergence and precipitation there. The distinct teleconnections between the SC precipitation and the tropical SSTs in the early and late rainy seasons can be well reproduced in the sensitivity experiments by an atmospheric general circulation model.