## 3 Results
### Adjusting the Algorithm to Regional Properties
#### 3.3.3 Climatic Events  
In addition to the dynamic and bio-optical properties, it is crucial to consider the impact of large-scale climatic events on the region's properties. Notably, discrepancies have been observed during ENSO events in the CCS [29]. The shifting boundaries between subarctic waters and tropical/subtropical waters during cold and warm events have been identified [17]. Such shifts, generally associated with changes in circulation and biological and chemical characteristics, necessitate an analysis of in situ data variations during these events. To classify the data, three distinct indexes were employed: the Southern Oscillation Index (SOI, [[https://www.ncdc.noaa.gov/](https://www.ncdc.noaa.gov/)]([https://www.ncdc.noaa.gov/](https://www.ncdc.noaa.gov/)) accessed on 12 December 2018), the Oceanic  
Figure 5: Retrievals of \(\log_{10}\) of mChl-\(a\), using Equation (8), for coastal waters (dotted line), Equation (9) for transitional waters (solid line), and Equation (10) for oceanic waters (dashed line), compared to the \(\log_{10}\) of in situ Chl-\(a\) data (red squares for coastal waters, green crosses for transitional waters, and blue circles for oceanic waters). Nino Index (ONI, [[https://origin.cpc.ncep.noaa.gov/](https://origin.cpc.ncep.noaa.gov/)]([https://origin.cpc.ncep.noaa.gov/](https://origin.cpc.ncep.noaa.gov/)) accessed on 12 December 2018), and the multivariate ENSO index (MEI, [[https://www.esrl.noaa.gov/](https://www.esrl.noaa.gov/)]([https://www.esrl.noaa.gov/](https://www.esrl.noaa.gov/)) accessed on 12 December 2018). Data were categorized as El Nino or La Nina based on the classification provided by any of the three indexes for the respective month and year. If none of the indexes indicated a cold or warm event for that period, the data were labeled as normal. Subsequently, a polynomial function was fitted for each condition, as depicted in Figure 6.  
In waters off the Baja California Peninsula, coastal upwelling determines the variability of the phytoplankton community [34]. Therefore, when there is a disruption in these patterns, i.e., during El Nino/La Nina events, biomass and community composition experience a shift. A warm El Nino event is usually associated with weaker alongshore northwesterly winds, deepening of the seasonal thermocline, and the near-shore poleward transport of warmer, nutrient-depleted water. Therefore, a decrease in diatom abundance and an increase in the small cell communities is expected. A cold La Nina event brings stronger winds and colder, nutrient-rich water, which tend to favor diatom growth [35; 36]. The extent of eutrophic and mesotrophic areas of the California Current during ENSO events has been analyzed, determining that there are important differences between the waters off of Baja California to those off the coast of California [29]. Furthermore, a reduction of the eutrophic and mesotrophic areas off the Southern California Bight associated with a decrease in upwelling was noted [29], along with an increase in the extent of the mesotrophic areas off of Baja California extending up to 700 km offshore, thus unlikely being due to upwelling but possibly to cyanobacteria. During the El Nino event of 1997-1998, Ref. [37] noted that in the region south of Punta Eugenia, tropical and subtropical waters dominated the region, while north of Punta Eugenia, there was a coastal poleward flow that displaced the core of the California Current offshore. Due to the large variability of this transitional region, both at the seasonal and interannual scales, one would not expect a global algorithm to adequately comprise the processes within this ecosystem. The analysis for interannual warm and cold events in Figure 6 revealed that most data have high \(\mathfrak{N}\) values and low Chlorophyll-\(a\) during El Nino. Therefore, during El Nino events, waters tend to be more oligotrophic, showing the expected shift towards smaller cells [36].