Gorgeous New York spring weather ushered Lifetime Achievement Award recipient Christo and nearly 400 supporters and guests into The National Academy for the Upper East Side institution's 2013 spring gala Thursday night. Artist-Academicians, including Carolee Schneeman, Alex Katz, Red Grooms and Wolf Kahn, donated work to the silent auction, which helped up the total amount raised for the evening to over $500,000. Chairman of the board of governors and National Academician David Kapp promised to use the funds to "keep this institution on its path of revitalization." First Deputy Mayor Patricia E. Harris and Art International Radio director and founder Alanna Heiss presented the award to Christo.   —Tracy Zwick